White Hot Flames
by HouseWarcraft
Summary: New to the Japan district, Calista is given the mission to keep a close on the Sons of Satan, to make sure they don't lose control...and to kill them if necessary. But can she do her duties, while keeping her cover and feelings in check? Takes place two months after season 1 ending. Rating may change as story develops.
1. Calista

**Hello all! I haven't written anything in a long time. This is my first attempt at a Ao no Exorcist/Blue Exorcist story. I'm still working things out, but this is the first chapter, likely the most boring, bare with me, it's mostly just introductory. This will take place two months after the ending of season 1 (yes I'm aware it isn't canon). Feedback is certainly welcomed and encouraged!**

 **I don't own any characters or Blue Exorcist. I only own the OC's created in the story.**

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This would be the first time she's ever been outside of Rome. While she was excited for the change in scenery, Calista wasn't here to sight see. No, she'd been given a mission to keep a close eye on a pair of demons working as exorcists inside the True Cross Order. Rin Okumura and his twin brother Yukio. Both were considered dangerous and unpredictable. Why she'd been chosen for this mission she didn't understand. Maybe it was because she was their age and half demon herself? Regardless, she had a job to do and she would see it through. If she found that either boys were a threat, she was to eliminate them immediately. Even though they already had more than one exorcist watching over them, they were now considered to be too close to the boys to perform their duties, should they need to be killed.

So they sent her with strict orders not to reveal herself to them.

She stood outside of True Cross Academy, starring up at the enormous school and wondered how anyone could possibly navigate their way around such a place. Was all of this really necessary? It seemed a little excessive to her.

"Seems like someone is compensating for something to me." Rolling her eyes, Calista readjusted the shoulder strap of her backpack. "Can't believe I have to attend school here and go through cram school all over again." Shaking her head as she spoke to herself, Calista made her way towards the huge school where she would get her classes and dorm room. First she needed to see Mephisto, the principal of this school and the only one who was to know of her involvement here.

It took her over an hour to find his office...having to ask more than once for directions. When she finally comes to her destination, she wasn't in the greatest of moods. Without bothering to knock, she enters the room, her aquamarine eyes blazing with annoyance. "Could you have made this place anymore confusing?!"

He looked up at her with his green eyes, just as annoyed by her barging in as she was by how confusing his school was. "My girl, it is rude to enter before knocking. Didn't they teach you any manners in Rome?"

"Oh shut it," She dropped her backpack on the ground beside a chair, before sitting down, crossing her legs. "You know why I'm here, and you know you're not to speak a word of my presence to anyone."

He waves a hand dismissively, passing a square piece of cheese to a little green hamster. "Yes, yes, of course. The Okumura brothers have no idea you're coming or your involvement with the Order. The only one who knows you're coming is Yukio, who is expecting a new student this afternoon. As I do not have any open rooms in the girls dorm, you will have your own separate room in the Okumura's building. I hope that will suffice?"

"Yeah, that'll be fine. This way I can keep a better eye on them without appearing suspicious." She stands back up, lifting her bag as she does. "As you well know, the Vatican doesn't trust you or them. That's why they sent me."

Mephisto held out a key that would allow her to access the cram school. "Of course, my dear, but I do wonder..."

"What's that?" She glanced back at him over her shoulder after taking the key and turning back towards the door.

"If they truly trust you, as you seem to think they do. Especially since you're no ordinary demon.~"

Calista didn't bother to answer him, instead her eyes narrowed into a glare.

She found the dorm building fairly easy. Then again it was the only building on the whole property that looked like it should be completely abandoned. The fact that it wasn't, was mind boggling. "You're kidding me? Students actually live in this dump? The whole place should be condemned!"

"Where do you get off on calling our building a dump?" The irritated voice behind her, announced the presence of another.

Turning around, Calista came face to face with who she suspected to be one half of the Okumura brothers. The one in front of her had dark blue/black hair and blue eyes. What stood out though, was the pointed demon ears, long black demon tail, and pointed fangs which were currently bared at her.

Before she addressed him, she had to remember to keep her cool and not give herself away. "Sorry," she apologized, giving him a small smile. "I didn't mean to offend you. I'm new here and just didn't expect to be placed in this dorm building."

He glared at her a moment more, as if he were trying to get a read on her. "My brother and I are suppose to be the only ones in this building."

She nods her head. "Yes, I was told that there weren't any empty dorms available in the girls building, so the principal placed me here until further notice." Remembering the custom in Japan was to bow when greeting someone, Calista quickly does so, so as not to further offend him. "My name is Calista and I just transferred here from Rome. I'm to start the cram school today as well."

His eyes seemed to widen a bit as she mentioned this. "So you're going to be an Exorcist too?" He smiled and uses his thumb to point at himself. "I'm Rin Okumura and I'm an Exorcist too!"

So this was the older brother then? She heard about him. Unlike his younger brother, Rin had been born with Satan's blue flames and struggled to control them, having already lost himself once before. This was the one that needed watching over the most.

"It's a pleasure to meet you, Rin." She looked down at her watch on her left wrist, checking the time. "Hey, do you think you could help me get to the cram class? I was given this key, but I'm afraid I'm terrible at directions." Which wasn't a lie, like earlier, she was easily lost. Especially in new places.

"Yeah! Sure! No problem. I was just on my way there now in fact." He walks to the door of the building, slipping the key into the lock and turning it. When he opened the door, it led into a hallway that didn't look like it belonged inside the building the door was attached to. "My little bro Yukio is our teacher."

"Mr. Okumura is expecting me, though I haven't had the pleasure of meeting him yet." As Rin enter the hallway, Calista followed behind him.

"He's alright, I guess. A bit of a know-it-all." Rin shrugged his shoulders, leading the way.

"I've heard he's a genius. One of the few to become an Exorcist at such a young age. A prodigy, so to say."

"Yeah, I guess so." He seemed a bit annoyed by this, placing his hands behind his head. "But he's not all that. I'll catch up to him before he even realizes it."

She felt his presence before she heard speak up behind them. "You have a long way to go before you catch up to me."

Both Calista and Rin paused in their tracks, turning around to face the one who'd spoken. As Calista looked at the boy behind her, using his finger to push his glasses back up, she instantly knew that this was the other brother; Yukio Okumura. His eyes were a deeper shade of teal than hers. Paler than his older brother, but taller and more mature looking. Beneath his left eye were two moles, and one under the right side of his lips. A pair of pointed demon ears poked out from beneath his dark brown hair and she could only assume that his tail was carefully tucked away under his True Cross Order uniform; unlike his brother who left it exposed. There was no denying that there were major differences between these twins. She could tell that in just the few minutes of being around them.

"Yeah, well, you heard me. I will catch up to you sooner than you think!" Rin stated confidently.

Though he went unnoticed, Yukio's attention on her. Earlier, Rin had watched her closely, but seemed to quickly dismiss her, whereas Yukio's eyes seemed to try and see right down to her soul. It was a bit unnerving, but she wouldn't let it break her resolve.

"You're the new student then, from the Rome district." He said it matter-of-factly, like a true instructor.

Calista nods and like with Rin, she bowed to him. "That's right. I'm Calista, recently transferred here. It's a pleasure to meet you, Mr. Okumura, I look forward to learning under you."

Yukio watched her a moment longer. She could tell he was suspicious of her. Which he had every right to be. She'd be suspicious too. "Very well, you're both late, so let's get in and get started." He pushed his glasses once more as he moved between her and Rin and into the class room.

Calista stood there for a second, Rin going on ahead of her and following his brother into the classroom, grumbling. So those were the Okumura Brother's. Rin would be easy enough to keep her cover around, but Yukio….well he would be a bit more challenging. She smirks to herself, and as she did, a pair of sharp canine fangs glinted in the low light, the thought of a challenge exciting to her. It had been a long time since anyone or anything had made her this excited.

Hiding her fangs, she too followed the twins into the classroom; eager to see how this mission would turn out.


	2. Secrets to Keep

**I've gone back through chapter one and fixed any mistakes that I was able to find after reading over it. Sorry for all of that, it was pretty late when I finished it and I wanted to get it up before I went to bed so I was tired, I'll try to proof read it from now on. I hope that you're all enjoying it so far and I would love to hear your thoughts, opinions and even what you think could make it better. Reviewing isn't required, of course, but it's certainly welcomed!**

 **I do not own Blue Exorcist or it's canon characters. I only claim the oc's created for the story.**

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Deciding that it was probably better for her to sit in the back of the classroom away from the other students, and away from the Okumura Brothers, Calista found an empty table that she would have all to herself. This way she wasn't right in their line of sight and likely to be forgotten rather easily. As the afternoon went on, she had to hand it to the youngest of the twins, Yukio was actually a pretty good teacher, keeping the attention of most everyone. Rin on the other hand, seemed to fall asleep more than he actually paid attention. It was a wonder that he'd made it this far.

Still, she couldn't blame him. Yawning, she leaned on her propped up hand. Of course she already knew all of this and because of her prior knowledge, found this whole thing to be rather boring. _"Ugh…when is it over?"_ She found myself thinking more than once.

"I think that will be all for today class." Calista heard Yukio say from the front of the class. When she lifted her head, she saw him packing the suitcase he'd brought in with him.

"Finally..." She whispered to herself, standing up and pulling her backpack on to her shoulder. She was ready to leave and get back to the dorm. By now her things should have been brought over from her own dorm in Rome. She could really use a hot bath and a soft bed. The time difference was finally catching up to her and she was more than a little exhausted.

Without even speaking to the other students, though she could feel their curious eyes on her, she left the classroom and headed down the hallway. Reaching into her pocket, she wrapped her hand around the key, Mephisto gave her earlier that day. It should lead her back to the dorms just like when Rin had opened up the door to the cram school.

Just as she was pulling the key out of her pocket, she heard someone behind her calling her name. She could only assume that it was one of the twin brothers, seeing as she didn't remember giving her name to anyone else. Pausing, she turns around to see that Yukio was waving her down and making his way towards her.

 _"Great, what does he want?"_ She thought to herself, putting on a fake smile before addressing him. "Hey there, Teach. Good class today, learned a lot. You're pretty good at this by the way." Her aquamarine eyes, looked up into his teal ones.

"Why were you sent to Japan, Miss..." He trailed off, realizing that she'd never given him her last name.

"Just Calista, I don't have a last name." As she informed him of this, the look of shock in his eyes didn't go unnoticed, so she explained a little further. "I was found as a baby and raised in an orphanage. They never bothered to give me any more than a first name." She shrugs her shoulders. "It doesn't exactly bother me either. So please, just call me Calista, besides, there's no need to be so formal."

He frowned, but seemed to accept this as he pushed up his glasses and nodded. "Very well then, but my question remains the same. Why were you transferred here?"

Time to make up another lie.

"You see, I have no idea why I was sent here." She said, "I was told that they could no longer house me in Rome and would instead be sending me to Japan. Why here of all places, I couldn't tell you. I was studying to be a tamer and will continue to do so here."

"A tamer, I see." He nods his head and continued talking, though she wasn't exactly paying attention, taking the moment to take in his features a bit more.

He and his twin brother shared very little of the same facial features; other than the demonic ones. His skin much paler than Rin's and there was a maturity in his eyes that Rin didn't have. He was much taller too; practically towering over her. Despite the moles on his face, it didn't distract from the fact that Yukio was a good looking guy. His eyes alone were beautiful. If it weren't for the stoic expression on his face, he'd be even more good looking than his older brother.

Shaking her head, she tries to erase the thought from her mind. She wasn't here to appreciate their good looks, she was here on a specific mission and she couldn't let herself become distracted. No matter what she need to keep her mind focused on the mission at hand. These two were the sons of Satan himself. They have both already lost themselves to Satan's powers, and Yukio has been possessed once already by the Dark Lord himself. What's to say it wouldn't happen again? She needed to remain vigil.

 _"Get it together, Calista!"_ She yelled to herself. Tilting her head up, she looked him in the eyes. "Yep, got it! Can I go now? I'm expecting my things to have arrived from Rome and I want to get a bath and unpacked before going to sleep."

* * *

 **Yukio's PoV**

 _"Had she even been listening?"_ Yukio thought to himself as he looked down at the new student who joined his class this afternoon. Mephisto had told him just two days ago that he would there would be a new student coming from Rome. Hearing that they would be from Rome, Yukio instantly suspected that the Vatican was sending someone to keep a closer eye on him and his brother. Looking down at the girl in front of him, he wasn't so sure now.

She looked around their age, maybe a year younger even. Not very tall either, much shorter than he was by far. Though, he did catch something about her that wasn't exactly usual. Underneath her jet black hair, he caught a pair of small pointed ears, much like his and his brothers. Was she part demon too? His speculation made him study her feature even more closely. Even though her ears were pointed, she didn't appear to have any more demonic traits. If she had a tail, she was keeping it well hidden, and she was careful when she talked too. If there were any fangs, she wasn't showing them off. Her eyes though...they were the lightest shade of aquamarine that he had ever seen.

Before he could question whether she'd heard him or not, Calista had turned around and placed the key in the lock, turning it and opening the door that would lead back to the dorms and going through. When she left the door open, he figured it was because she was sharing the building with him and his brother. Sighing heavily, Yukio using his finger to push up his slipping glasses. This girl was a total mystery. He wasn't buying any of it. There had to be a reason why Rome had sent her here? He just needed to figure it out.

Someone slapped him hard on the back, pulling his mind back into reality and forcing his glasses to slide down on his nose once more. "Whatcha standing around for, little bro?" Rin's voice asked as his arm came around Yukio's shoulders. He looked through the open door, watching a moment as the new girl walked down the hallway of their building. A mischievous grin pulled at his lips, showing off the pointed caines. "Ohhh I see." He chuckled. "You're checking out the new girl, aren't ya.~"

Annoyed, Yukio's brow twitched. "It's not like that!" He yelled at his older brother, once more fixing his glasses. "I was just wondering why she was sent here. It's a bit suspicious." He then said in a calmer voice. "Never mind, let's go." Shrugging off Rin's arm, he moved forward through the door and back into their dorm building.

"What's gotten into him?" Rin questioned as he watched his little brother walk off, following the new girl into the dorm. Shrugging his shoulders, he follows along too, closing the door behind him as he does.

* * *

 **Calista's PoV**

By the time she had bathed and unpacked most of her stuff, it was well after sundown. Sitting on her now made bed, she looked down at the black and red hound laying by her feet. She had been telling Yukio the truth when she said she was studying to be a tamer...Well half truth anyway. She was already a full fledged Exorcist and Tamer and the hound at her feet was her familiar, Cerberus; named after the Greek hellhound who guarded the underworld. He didn't have three heads like the hound of myth, but he was a demon hound and she found it funny to name him after the legendary hound. Her Cerberus however, had black fur, tinged with red, his ears and tail crimson at the tips. He closely resembled the doberman breed. He was a bit of a pain in the butt at times, but he's been with her for years now and she loved him all the same. He was her closest friend and companion.

After she unpacked most of her stuff, she used the summoning tattoo on the underside of her wrist to summon him to her. It was easier than trying to explain him right away to a bunch of people she'd never met, and even harder still to explain to her teacher that she'd mastered summoning her familiar already when she was suppose to be a newbie. She'd just use summoning papers to bring him to her when she was around everyone else. If things ever got hairy and her paper weren't within reach or destroyed, she could use the tattoo on her wrist, and risk explaining if the time came.

Reaching a hand down, she lightly patted him on the head, rubbing his ears. He lifted his head and looked up at her with his dark, red eyes. _"Why are we here again?"_ He asked her. Because she was a demon, she could hear him and easily communicate.

"You know why we're here, now keep your mouth shut about it. Our targets are both demons and will be able to hear you when you talk to me. We have to keep our mission to ourselves. No one is to know about it." She glared back down at him, trying to appear fierce, but failing when her stomach gave a loud growl.

 _"You're hungry...when was the last time you had something to eat?"_ There was a look of concern in his eyes. He tended to worry about her wellbeing, which was a good thing, because she didn't do the best job of looking after herself.

Calista tapped her chin in thought. "I think I had something earlier this afternoon before coming here. A bag of chips, I think. It wasn't much, I know that. I should probably go down and find something more to eat." Getting to her feet, she walks over to the door, slipping her feet into a pair of black flats.

Behind her, Cerberus stood up and glared at her, growling low in his throat. _"You know what I'm tal-"_

"Are coming along? I'm sure you're just as hungry as I am?" She asked, cutting him off mid sentence. Before he had the chance to question her again, Calista opened the door and walked out of her room. As she entered the hallway, the smell of something cooking immediately caught her attention. Her mouth watered and she follows the scent all the way down the hall until she came upon the kitchen.

Peeking around the corner, she looked into the kitchen. She saw several tables with chairs, but what surprised her was Rin Okumura was standing in the middle of the kitchen, moving back and forth, cooking something and working his butt of doing it. "I had no idea he could cook..." She whispered to herself. Upon closer look, she could see that he wasn't alone. On his shoulders sat a two tailed cat, and on the counter was a purple, satyr-like, demon.

Her stomach growled again, and when it did, the cat sitting on his shoulders turned his head and looked back at her, meowing he pawed at Rin's cheek. _"Rin, someone's watching from the hallway."_ She heard him saying.

"Huh?" Rin questioned, looking back at the cat, before looking over his shoulder. Catching sight of her standing there, he smiled and waved her in. "Come on in, it'll be done here soon." He said this rather excitedly.

Deciding to go with it, Calista entered the kitchen and took a seat at the counter that looked into the cooking area. As she sat down, she noticed that Cerberus had in fact, followed her. When she looked down at him, he was glaring at her. She knew what he wanted to say, but was glad that he kept his mouth shut. Turning her attention back to Rin, she questioned him about what he was make. "So, what are you cooking?"

He grins from ear to ear. It was obvious by his expression that whatever he was making was something he was proud of. "Since you're new here and all, I thought it would be a good idea to make my favorite; sukiyaki!"

"Suki...yaki?" She was a bit confused, having no idea what kind of meal this was. Having been born and raised in Rome, Calista was more use to Italian foods than Japanese. Only having Chinese fried rice, or noodles every now and then. Her extent of Japanese food was what she saw in anime and that was mostly ramen, which was available in supermarkets around the world. This, sukiyaki, was completely new to her. But she wasn't a picky eater and would try anything once.

"Yep!" His smile widens even more. "It's amazing, you're gonna love it!"

Calista chuckles a bit at his enthusiasm. "I'll take your word for it." Looking around the kitchen, she wondered where the younger of the twins could be. "So, where's Yukio? Shouldn't he be here to eat dinner too?" Absently, she places her hand on the top of Cerberus's head, lightly petting him as she talked.

By now, Rin had turned around and went back to his cooking. "I think he said something back taking a bath." He shrugged his shoulders. "I'm sure he'll be here later on." As Calista nods her head, Rin went on to ask a question of his own. "So, were you sent here to watch over my brother and I?" He asked this without even turning around to look at her.

The hand petting Cerberus immedately paused, but her expression remained the same. "What? No, of course not. It's like I told Yukio, they were unable to continue housing me and sent me here. It's not like I had a choice in the matter." She propped her elbow on the counter, placing her cheek on her hand, trying to take on a "bored" look. Maybe it wasn't going to be so easy fooling either of them after all?

"Good," His voice took on a more menacing tone. "If you were here to hurt my brother," He turned around and there was a look in his eyes that sent a shiver down her spine. "Then I'd have to kick your ass." Rin made no mention of himself, only that of Yukio, like a good older brother would. If it had been anyone else, she might have laughed at him, but the look in his eyes, the tone of his voice, and the fact that he was Satan's son, kept her from feeling any kind of amusement. He meant every word that he said.

She'd have to tread carefully...

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 **Alright, well there's chapter two. Not much going on again, but I like to build up before jumping right into the action/romance. Don't worry, it'll happen, but not overnight. Haha. Anyways, I've skimmed through it for any errors, but will look over it more carefully tomorrow after work. Remember, I love feedback!**


	3. The First Mission

**Hey all. Sorry for not updating recently. I've been working and it's been an exhausting couple days. So here's the new chapter, I hope you're all enjoying it so far; I know the first two chapters have been a little slow to start, but all good stories start out slow before picking up. I'm going to try and start getting into the main plot and explaining a little about Calista's origins. After that, I'm hoping to get to building the chemistry between our main pairings. :3 Now I'm not going to waste your time any longer, on to the story.**

 **I do not own Blue Exorcist in any way, I only claim the oc's created for this fanfiction.**

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 **Calista's PoV**

The first class mission came in three days later. For the most part, she'd been able to avoid Yukio and Rin, only seeing them at meal times and during cram classes. She found out that Yukio was just one of their teachers and that there were several others, including swordplay; something she wasn't exactly good at, relying mostly on her hellhound and the pistol she keep hidden on her upper thigh, just underneath her skirt. Normally she had her weapons within easy reach on her side's, using a shoulder holster to carry her pistols, but she wasn't suppose to be anything more than a normal student and normal student don't yet carry weapons like hers.

Their mission was to take place in the middle of the night. Apparently there has been complaints of unknown mischief going on. From the sounds of it, the demons involved were nothing more than low level goblins. For her, this mission would be a piece of cake.

Yukio broke them up into groups of two. She'd been assigned to go with some girl named Shiemi who had a little greenman as a familiar. One thing Calista instantly noticed about her was just how shy and nervous she was. She didn't talk much, outside of asking which way they should take. As soon as they were away from Yukio and the red headed boob girl, she planned on ditching her partner and going out on her own. Goblins were nothing.

It didn't take much to lose Shiemi, ordering Cerberus to run off ahead of her, making it seem like she had to chase the hound down, calling out to him. Couple turns, and she had lost her. Crossing her arms, she leaned back against the wall of a building, sighing heavily in annoyance.

"This sucks…I'm a full fledged Exorcist, pretending to be an unskilled newbie. It's a disgrace to my skills." She complained.

" _When are you going to take my advice, and feed yourself? The longer you go, the weaker your body becomes. You're not at your full strength. How do you plan to take on the demon twins when right now you're neglecting your own needs."_ Cerberus growled at her, snapping his jaws, demonstrating his frustration.

Calista glared down at him. "Would you shut it already. I'm fine and I don't need you reminding me." She pushed off the wall and head down the alleyway.

Of course Cerberus follows her. _"If you're not going to look out for yourself, someone has to."_

Though, he had a point. She'd gone several days at this point without properly feeding herself. If she went any longer, she was likely to get herself hurt, or someone else. "I'll deal with it after we're through here. I can't let anyone catch me, so I'll go out again after everyone's gone to bed. Is that alright with you?"

He nods his head. _"That will suffice."_

Nodding her head, Calista sighed and placed her hands behind her back where she clasps them together. She didn't intend to do any of the goblin hunting that the mission called for, but instead she found a rusted old ladder and began climbing up towards the house roofs. At this height, she'd be able to keep a an eye on things that were going on below. It was easy enough going from rooftop to rooftop, her demon blood allowing her to do things that most humans couldn't and right at her side, Cerberus followed obediently.

When she found a few of the students, she was careful to go unseen as she followed them. Her turquoise eyes showed her amusement at watching them handling any demons they encountered. Honestly, she had to hand it to them, they were decent. At the rate they were going, they would all easily make full fledged Exorcists in no time at all. Even though she paid attention to the human students, she kept a close eye on the oldest of the Okumura brothers, waiting and wondering if he would pull the demon sword from it's sheath, igniting those blue flames. From the reports she read prior to coming here, Rin relied heavily on his demon powers tied to the sheathed sword in his hand. It was only a matter of time before he pulled it, for a bunch of low level hobgoblins.

" _Eventually he's going to mess up…I know it."_ Calista thought to herself as she watched from the roof of the building.

For a moment, she turns her attention away from the older twin, searching for the younger of the two. It took her longer to find him. It seemed he decided to stick back and watch how is students did on their own. From this height, she was able to watch him without him having his guard up; on his own, he let his emotions slip through.

There was noticeable tension in his jaw; something was causing him quite a bit of stress. She knew that it couldn't be his brother, seeing as he was off with his partner exorcising any demons that crossed their path, so what could it possibly be? She got her answer when his left arm suddenly caught fire. Her eyes widened at the sight of those infamous blue flames and at the same time, she realized that he was struggling to maintain control of them. Unlike his cool, calm, exterior, Yukio fought to keep his flames in check.

" _This is interesting,"_ she thought to herself, a light smirk on her lips. _"It would appear Mr. Collected, isn't quite collected after all."_

While she watched Yukio, her thoughts distracted, Calista let her guard falter. Behind her a large and unusually strong goblin appeared out of thin air; going unnoticed until it was too late.

" _Calista, behind you!"_ Cerberus called out to her, immediately going on the defensive and attacking the demon.

Hearing her familiar's warning, she began turning around to defend and attack, but before she could pull any weapons, the Behemoth lunged at her; her hellhound had his jaws firmly attached to his arm. "Shit…!" Being the on the edge of the building, she had little room to maneuver and couldn't get out of the way quick enough. As the demon lunged, she took a step back, only to feel her foot slip on the edge. Her eyes widened as she felt her foot slip and suddenly she was falling from the roof of a three-story building. There wasn't a lot in this world that terrified her, but at the top of her list, falling was the most terrifying.

A gasp of fear was pulled from her throat, the air in her lungs rushing out. She could feel the "weightlessness" of her body rushing towards the ground below, her stomach in her chest. Even though she was half demon, a fall from this height, would leave her seriously injured. Closing her eyes tightly, she braced herself for the pain that she knew would be coming.

* * *

 **Yukio'S PoV**

Somewhere above him, Yukio heard someone calling out a warning. The voice was in his head, one that no one without demon blood would be able to hear. "What the...?" He questioned out loud, tilting his head up to try and see who it was. His eyes widened though, when he saw a girl falling from the roof of the building above him.

He didn't have time to think about it, his body reacting before he even got the chance. Eyes narrowing, he put out the flames that had engulfed his left arm and leapt towards the falling girl. At the same time that he caught her against his body, wrapping an arm around her to keep her secure, he pulled one of the two guns from the holster at his back. Taking aim at the large Behemoth goblin coming towards him. At the last second, he realized that there was a hellhound attacked to it's arm. Readjusting his aim, he fires two rounds, hitting the demon right between the eyes, effectively killing it.

With the demon dead, Yukio landed back on the ground, looking down at the girl he'd caught; realizing then that it was his new student. _"What the hell was she doing up there on her own?!"_ Just as he was about to voice his question out loud, he noticed her eyes were shut tight and her face was paler than usual, making it easy to tell she had been terrified.

Taking a deep breath to calm himself, Yukio careful let her feet touch solid ground. "You're safe now..." When he felt she had her balance, he let her go fully. "What were you doing up there on your own? I thought I assigned you and Shiemi to work together as a team?"

Even though she was now safe on the ground, Yukio could see that she was still shaking. Did she have a fear of heights? Still, she pulls herself together rather quickly, turning and looking up at him, only to look away once more, avoiding eye contact with him. "Yeah well, Cerberus ran off and I had to chase after him. At some point, Shiemi and I got separated and I climbed to the roof to see if I could find everyone quicker than looking on the ground." He listened to her explanation, noticing her cheeks darkening as she blushed in embarrassment. "That demon caught me off guard and my foot slipped off the edge."

An accident then...

Sighing, Yukio using his finger to push up his glasses, keeping them from slipping down his nose. "Fine, but you should learn to control your familiar a little better. If this was a real battle and he had run off, separating you from the group, you could have been seriously injured by a more powerful demon."

Calista too sighs, but she seems to accept his chastising with a simple nod. "Yeah, alright, it won't happen again." He watched her pull out the summoning paper from her vest pocket, holding it between her fingers and tearing the sheet, releasing the hellhound. "If it's alright with you, I'm going to head back to the dorm. That fall left me a little shaken..."

He found it a little odd that she refused to make eye contact with him. Maybe she was just too embarrassed for making such a mistake. "Alright fine, you're dismissed for the night. Let this be a lesson to always stay aware of your surroundings."

She nods her head once more, but doesn't say again. When she turned around to leave, something caught his eyes. Were those...? His eyes had gone wide. Her ears...they were pointed! He was certain of it. It had been brief, but he HAD seen them underneath her hair when she turned. Did that mean she was half demon too? Was that why she'd been sent here? Shaking his head, he brushes the thought aside. No, it was just a coincidence.

He watched her leave until she was completely out of sight. Only then did he turn his full attention back on his other students. It didn't take them longer, clearing out the goblins quickly on their own. While there had been some mistakes, they had all performed really well. Calling it a night, Yukio and Rin head back to the dorms together. Rin going on and on as usually, but he couldn't get the new girl out of his thoughts. For days now she's been invading his waking mind. Who was she and why was she here? Seeing what he thought were demon ears on her tonight, only increased his curiosity.

Yukio and Rin arrived back at the dorms around an hour after Calista left. "Man I'm hungry!" Rin complained. "I'm going to the kitchen right now making a bowl of-" A window broke from the second floor, cutting Rin off.

"What the hell?!" Yukio didn't hesitate, running inside, pulling both of his guns as he and Rin rush inside. Did a demon get inside? "Calista!" He calls out to their new dorm mate, after tonight's incident, he worried that she wouldn't be able to handle a higher level demon on her own. Rounding the staircase, he takes them two steps at a time, knowing Rin was right on his heels, ready to pull his sword at a moments notice.

"Calista!" He calls out to her again as he comes up to the second floor.

The entire landing was covered in darkness, not one light on. He couldn't really see anything. Turning his head left and right, he tried to listen for anything that could indicate that there was a threat and where it was. When he turned his head to the left though, Yukio froze. At the end of the hallway, a pair of glowing crimson eyes stood out, glaring at him and his brother.

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 **Hope you enjoy this chapter, took a little longer than I expected, but as stated above, I've been fairly busy. Remember to send in those reviews!**


	4. Losing Control

**This chapter will be entirely in Yukio's PoV. I really hope that you're all enjoying it so far. Remember to send in those reviews! I love hearing your feedback.**

 **I do not own Blue Exorcist/Ao no Exorcist in any way.**  
 **I only claim the oc's created for this fanfiction.**

* * *

"What the hell is that?!" Rin yelled out, holding the demon sword in both of his hands, getting ready to pull it from it's sheath if he needed to.

"I have no idea, but keep your guard up." Yukio said to his brother, moving the guns forward, aiming at the pair of crimson eyes.

Whatever was at the end of the hallway, took a step toward them, a low growl emitting from its throat. It was then that both Yukio and Rin heard a voice speaking to them. _"Put your weapons away."_

"Reveal yourself!" Yukio yelled out to it. Seeing as he could hear the voice in his head, but not out loud, he made the assumption that whatever this was, it was some kind of demon.

It growls again, this time barking. Wait…barking? While the dorm building was completely dark, the moon outside was full, and as the clouds moved from in front of it, light shined through the windows, illuminating the darkened hallway. His eyes quickly adjusts to the changes in lighting and he sighs in annoyance as he sees who was at the end of the hallway. It was Calista's hellhound familiar, Cerberus.

Lowering his guns, but not holstering them, Yukio approaches the beast. "What the hell is going on here? Why are the lights out in the building and why did the window break?"

The creature didn't say anything more, instead he turns around and heads into Calista's room, the door wide open. Yukio glances back at Rin, who shrugged his shoulders, just as confused as he was. Since there didn't appear to be any threats in the building, Yukio places the guns back in the holsters at his back. He still wanted answers though, and so he follows Cerberus into the room, pausing just outside to address his brother. "Why don't you go down and check the breakers? Maybe they were overloaded and this is all just an odd coincidence."

"If that's the case, why are you following her demon into her room?" Rin asked, placing the sword back on his shoulder, glarring annoyingly at his younger brother.

"Because there's still the case of the broken window. I'm going to see if she's got any answers, if there's any problems I'll call you right away."

Rin stood there stubbornly, "Tch, whatever." He growls, turning around and heading back down the stairs and to the basement where the breakers were located.

Sighing at his brothers stubbornness, Yukio shakes his head. Facing the opened door once more, he politely knocks before entering. "Calista?" He called to her, much like he had as he raced up the stairs, though this time his voice was calmer, no longer thinking one of his students were in danger. Coming into the room, as with the rest of the building, the lights were out, the light from the full moon outside allowed him to walk without bumping into anything.

At first, he didn't see her anywhere, but the closer he looked the easier it became to see in the low lighting. Her room was mostly bare, with random pictures and posters hanging on the walls. There were still a few boxes left unpacked. Turning his attention away from her personal objects, Yukio looked around for her again. His eyes landed on the hellhound sitting in the corner. "Where is she?"

His lips pulled back from his teeth, and he growled much like he did in the hallway. Only this time, he didn't give him the silent treatment. _"Get out, Son of Satan. We do not require your presence."_

 _"Wait, how did he know that?"_ Yukio's eyes narrowed again, something was up with this pair, he just knew it. "I'll ask you only once more," Reaching behind him, he pulls a gun from the holster, aiming it at the growling beast. "Where's your master?" His voice was stern, the moonlight gleaming off his glasses.

 _"Why you little..."_ His growl deepens and he stands on all four paws, lowering his body as if readying to attack.

"Cut it out, Cerberus..." Calista's voice spoke up from behind him. "Stop trying to protect me all the time."

There was something about her voice; it sounded strained. Yukio looked over his shoulder, his eyes narrowing when he saw her crawling out from underneath the bed. She looked like hell...What was going on here? While she'd been pale earlier, he shrugged it off as her fear from falling off the roof, but now it appeared that there was an underlying cause. Narrowing his eyes, and tensing his jaw, Yukio walked over to hold out a hand to her, offering to help her up. "I think it's time you answer my questions."

She lifted her head to look at his outstretched hand, though she still avoided eye contact with him. "Yeah..." Taking his hand, she accepted his offer for help.

When she was sitting on her bed, Yukio took in her outward appearance a little better, or as best as he could in this low light. Grabbing the chair at her desk, he takes a seat in front of her. "Alright, let's start with why you're really here." As he questioned her, his eyes scanned over her. Not only was she pale, but her skin seemed sunken in. Her breathing was a little labored, like she was having trouble, or that the simple movement from the floor to her bed had taken a lot out of her. Either way, she was struggling. He could see that her hands were clasped together tightly on her lap, and even though it was subtle, he could tell they were shaking.

"The Vatican sent me here...to finish my training as an Exorcist..." She takes a deep breath, her voice just as strained as a moment ago, each word she spoke seemed harder to get out than the first. "Also...They didn't want a half..." She paused, her hands clenching together even tighter. "They didn't want to continue housing a half-demon."

 _"I knew it."_ His assumption had been right, those were demon ears he saw underneath her hair. "I see..." Was this really the truth? The whole truth? He couldn't tell for sure, her shaking hands would have normally given it away that she was lying, but he didn't suspect that her shaking was from not telling the truth. There seemed to be something wrong with her health wise. "Now, about your health."

"I'm fine." She quickly retorted.

"You're not." He glared at her. "You're pale and shaking. Your voice is strained. It's obvious that you're not okay. Stop acting all tough and stubborn."

"I told you I'm alright!" She yelled looking up at him, and this time he caught a look at her eyes. They were no longer the light shade of turquoise, but tinted with crimson. This caught him off guard, his own eyes widening, seeing the sharpened fangs in her mouth as she yelled.

Yukio quickly gained his composure, his hands clenching into tight fists, she was acting a lot like Rin. "You're obviously not! Suck it up and let someone help you, damnit!" If she was going to act like his brother, than he was going to treat her the same way. "Quit acting like a brat!"

"I'm not acting like a brat!" She stands up, surprising him with how fast she could move in her condition. "I'm trying to prote-" Her words were cut off when the lights suddenly turned back on. Tilting her head down, her bangs shadowing her eyes. "Just leave me alone, alright?" Her voice softened up and she walked past him, grabbing a towel and a change of clothes.

He watched her as she leaves the room. She was just as stubborn as his brother. Shaking his head, Yukio pinched the bridge of his nose, pushing his glasses up, sighing in frustration. "She's just as bad..." He whispered to himself. "I have enough trouble babysitting Rin..."

 _"She doesn't need babysitting."_ A voice behind him said.

"Huh?" He'd completely forgotten that Cerberus was still in the room. Turning around in the chair, he looked at the demon hound. "What are you talking about, she's obviously just as bad as my brother in temperament."

His rolled his crimson eyes, circling the spot in the corner, before laying down. _"She's just hungry. This is the longest she gone without properly feeding herself. If she doesn't get a grip soon and do what needs to be done, her body will eventually force her to do so."_

Yukio had no idea what he was talking about, he'd seen her eating at every single meal. "How can she be hungry? She eats with us at every meal."

Cerberus lifted his head and looked at him, then looked at the door, only to look at him once more. _"Fine, to keep her safe, I'll tell you."_

Yukio listened closely. When he finally made it to the point, his teal eyes went wide with shock. "Y-you're kidding me?!"

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 **Let me know what you think so far! Until the next chapter, my lovely readers!**


	5. Just A Little Taste

**So here's the next chapter. You'll learn more about Calista and who she is. This is my longest chapter yet and I hope that you're not dissatisfied with the way it's come out. Let me know what you think! Reviews are always welcome and encouraged!**

 **I do not own Blue Exorcist/Ao no Exorcist**

 **Only the Oc's created for this fanfiction**

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 **Calista's PoV**

With the power back on, Calista was able to take her bath, one she desperately wanted; the warm water usually helping her to calm down at the end of a day. With the water at the temperature she liked, Calista sinks up to her chin, closing her eyes as she sighed. Her entire body felt really tense, like her muscles had been overworked. "Man I hate when it gets like this..."

 _"Suck it up and let someone help you, damnit! Quit acting like a brat!"_

She gasps out loud and sitsup straight, water splashing over the tub and onto the floor with her jerking movements. Yukio's face and voice invaded her thoughts. "Damnit..." Shaking her head and closing her eyes again, she tries to force him from her mind. She didn't need that glasses wearing, know-it-all, telling her what she needed to do. Once she got him out of her head, she opened her eyes again and pulled her knees to her chest, wrappingher arms around her legs, andholding  
them there.

Her stomach clenched tightly and it made her groan in pain. Tightening her arms around her legs, Calista placed her chin on top of her knees, staring into the water. What was she going to do? If she stayed around these two, she would eventually be found out, and then she'd be seen as even worse than the Son's of Satan. Gritting her teeth, she refused to let either one of them figure her out.

"I'll go out tonight, as soon as everyone is asleep...There's got to be a butcher's shop somewhere in town. I'll just grab some from there and it'll get me through at least a couple of days. Once the weekend comes, I'll have more time to be on my own...then it won't be so suspicious when I go out in the middle of the night." She spoke in a hush whisper, although the bathroom walls still made her voice echo. Thankfully, she was the only female in the entire building.

With another sigh, Calista let her legs go and sunk back underneath the water, this time completely submerging herself. Holding her breath, she stayed under as long as her lungs would allow. When she reached her max, she quickly surfaces again, taking in a lungful of air, andsweeping her drenched hair back away from her face. Not wanting to spend any longer than she needed to in here, Calista finished her bathing, washing herhair, face and body. Grabbing her towel, she wraps it around  
her, letting the water drain as she sits on the side of the tub.

The water finished draining, and she continued tositthere for several more minutes. Her hands curled up into tight fists, before she spoke to herself, "Stop wasting time...just get dressed and go back to your room."

It took her a half a minute more, but she eventually did get up and get dressed. Wringing her hair out, she pulls the wet strands up into a tight bun on the top of her head. With her hair up like this, it left her pointed ears exposed. Now that Yukio knew the truth about her being a half-demon, she didn't see the point in hiding it anymore. She was glad that she didn't have to deal with a tail like those two did.

Carrying her wet towel, and dirty laundry, Calista leaves the bathroom. She could hear someone in the main kitchen just down the hall. Figuring it was probably Rin making lunches for the next day, she decided not to pay it much attention, instead ignoring him and going back to her bedroom. Certain that Yukio was long gone, she entered the room speaking openly to Cerberus while hanging the towel on the rack behind her door.

"Once those two have gone to bed, I'm going to head back out and find a butcher's shop. What I can get in there should be enoughto get me through the remainder of the week. Then this weekend, I'll figure out something better. Will that be enough to get you off my back?" She asks him, turning around to see him, only to find Yukio Okumura sitting in the same spot she'd left him. "W-what are you still doing here?! It's been over an hour!"

She noticed that his coat was off, leaving him in the white shirt and black school pants. His arms were crossed over his chest, and legs crossed as well, his face cold as stone. "I can't let you leave this dorm, not in the condition you're in. You're likely to hurt someone." He said it as a matter-of-fact, his voice calm despite the look on his face.

Her eyes narrowed and her hands turned into fists at her sides. "What the hell are you even talking about? You don't know anything about me and you can't keep me here just because you're a teacher."

He used his index finger to push his glasses back up his nose, a gesture he seemed to do often. She didn't wear glasses, but she started to feel that he did it excessively. "I know everything now and knowing about your secret, I can't let you leave here in the condition you're in." He repeated.

"W-what? How could you possibly know anything?!" She glared at him, only to see the hellhound behind him sleeping away. "You...You told him?!" Cerberus opened his eyes and lifted his head to look at her, only to lay his head down again, ignoring her.

Yukio suddenly stood up and took a step towards her. "If what your familiar has said to be true, than letting you leave like this makes you a danger to everyone."

Calista took a step back from him. Why was she suddenly intimidated by him?! "I think I know better than you about how to handle my own needs! I don't need you telling me about being a danger!" She took another step back, turned on her heel and went for the door. She wasn't going to let him scare her! "I don't need you to look after me! I'm out of here!" She got the door open, but before she could take one step out, she felt his hand grab her wrist; his hold firm, but oddly gentle. Looking back at his hand around her wrist, she pulled hard, trying to get free, yet only hurting herself in the process. "Let me go, Yukio!" Had she been at full strength, she probably could have freed herself easily.

"I told you, I'm not letting you leave here in the condition that you'rein. If anyone got hurt or killed, it would be on me." His voice was still oddly calm. How could he possibly be this calm when she was literally fighting to get free of him.

"If you don't let me go, the only one going to get hurt is you!" She knew her limitations, she knew how much she could and couldn't take. She wasn't new to this, having lived with it her entire life. In the beginning, before she could control her urges, she killed nearly everyone she came across. Hating herself with every day that passed, starving herself and only making the cravings worse. It wasn't until she'd been found my an Exorcist meant to kill her, that she was finally about to get control  
over herself. After that, she never lost control again...and dedicated herself to becoming one of the youngest Exorcists ever, soshe could help others like herself.

"I don't care..." This took her by surprise. He didn't care if she hurt him? Was he stupid...? "As your teacher, I'm here to help guide you and help you in any way that I can." His hold on her wrist loosened and then let her go completely. She watched him, her hand on the doorknob, ready to bolt, but his next move kept her standing there.

Yukio unbuttoned the two top buttons of his school shirt, exposing his collarbone and throat. His skin was pale and so smooth, she found herself staring at the throbbing artery in his neck, the one that supplied blood the brain. In her mouth, she felt her already sharpened canines, lengthen and sharpen even more. Closing her eyes she shakes her head, trying to pull herself together. "What the hell are you doing?" She asked, her voice slightly strained.

"Haven't you been listening, or are you as hard of hearing as my brother?" There was annoyance in his voice. "I'm going to help you, stop being so stubborn and thinking you can handle everything on your own. It's obvious that you're struggling."

"You don't know what you're doing..." She shakes her head again, refusing to open her eyes and look at him. "I can handle this. I don't need your hel-"

She was suddenly cut off when she felt his hands grabbing her upper arms and her back hitting the door behind her, slamming it closed the rest of the way. He did it with such force, that the breath rushed from her lungs, causing her to gasp. When she opened her eyes and looked up at him, she saw a side of the younger Okumura brother that she had yet to see; one she only saw from the older of the two. His eyes were a deeper shade of teal, almost blue, and at their centers were crimson.  
His brows were furrowed in an expression of outrage and pent up aggression.

"Just shut up, damnit!" He yelled at her, his voice deeper then before when he'd been arguing with her. "You can't always do things on your own! You have to let others help you!" Letting go of her, he stands close, his shirt partially opened, exposing his neck to her. Lifting a hand, he pulls it to the side, further exposing his throat along with his shoulder. "Now shut the hell up and feed already!"

 **Yukio's PoV**

Yukio glared down at her, his temper already slipping through. If he wasn't careful, his flames were likely to ignite. He was struggling himself,in controlling his flames, but had a hard time taking his own advice and seeking help. Not wanting anyone to look at him differently, or the way they often looked at his brother; with fear in their eyes. Pushing those thoughts to the side, he came back to the matter at hand.

After Cerberus had explained everything to him, he had to admit that he was completely stunned. Never had he heard of a vampiric demon before, much less a half bred one. From what the hellhound had told him, Calista had been found as a child of 4 or 5 by an Exorcist who'd been sent to take out the demon who was killing thepeople of their village. Someone would go missing every few nights, only to turn up with their bodies drained of blood. When the Exorcistfound her, she'd been unable  
to kill her target, instead bringing her back to the Vatican and raising her, much like his father had raised him and Rin. Even though there has never been an incident again, Yukio wasn't taking any chances in letting her leave here and cause harm to anyone, not until he was certain she'd be able to control herself. If feeding her his own blood would achieve that, then so be it.

 _"As long as it's either human or demon, it doesn't matter. Animal blood will suffice for a day or so, but the cravings will come back stronger than before. She must consume blood to stay at her strongest. Once every couple weeks, or she'll become weak from hungry. Today marks 3 months since the last time she's fed." Cerberus explained in detail the nature of Calista's demon side. "She hates this side of her and pretends it's not there, waiting as long as she possibly can."_

He understood all to well the hate she felt towards her demon half, hating his own every single day...

"Don't just stand there!" He yelled at her again, bringing his focus back on her, and her's on him. "You're not leaving this room until I know you won't be a danger!"

He could see that her eyes were practically glued to his exposed neck. The feeling of her eyes on him like that, made his mouth dry and his throat tighten up, he could even feel the blood rushing to his face and making him blush. Even though it was something that he never imagined himself doing, Yukio couldn't help feeling some kind of rush go through him, one that he tried very hard not to linger on. _"Hurry up before I change my mind...!"_ He said to himself, wanting her to get on with it before  
he chickened out. _"What the hell am I doing?!"_

She made the smallest of movements, but it was enough to grab his attention once more. He thought he heard her whisper something, but before he could ask her to repeat whatever it was that she said, she was taking another step closer, now putting them just inches apart. Yukio swallowed the lump in his throat, and even if he wanted to say something, he didn't think he would be able to. She stood on her tiptoes and her arms came around his neck, resting loosely on his shoulders, pulling herself up and even closer to his neck. He could now feel her warm breath against his skin and he closed his eyes, readying himself for what he knew would come next.

When she finally "sunk her fangs into him", Yukio was surprised that it didn't hurt like he imagined it would, or like it was portrayed in his horror manga. Instead, it was more of light pinch and then...His blush darkens even more, turning his entire face red. The sensation of her mouth against his neck, warm and wet, was one of pleasure. Her tongue licking his skin as she sucked was something he's never felt before and as she continued to drink from him, he found his arms coming around her body and holding her against his chest. She was small, not just in height, but her waist too. Tilting his head down, giving her better access to his throat, he breathed in the scent of her shampoo. _"She smells incredible."_ He thought, his arms tightening around her even more.

Her arms around his neck tightened just as his around her body did, and as they held each other in an embrace, Yukio's thoughts began to wonder, just as his hands did. Moving from her lower back, up along her spine. As he got higher, he could tell that she hadn't put a bra on after her bath. He felt a small smirk pull at the corner of his lips. His hands began to move back down again, gliding over her back and he felt her shiver at his touch. Wanting to get the same reaction out of her again, he got a little bolder; moving his hands underneath the edges of her shirt, wanting to feel her bare skin beneath his palms.

"Hey! If you're hungry, I fixed us up something!" A loud bang sounded on the outside of her door as Rin's voice interrupted them.

Immediately, Calista pulled out of his arms, turned her back to him and lifted a hand to wipe at her mouth. She didn't look back at him when she spoke. "The puncture marks will disappear by morning. I didn't take much, so it shouldn't affect you in any way." Before he could even say anything, she was out the door, leaving it open for him.

 _"What...just happened...?"_

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 **Well there it is! The first real interaction between Yukio and Calista! I hope you enjoy that small lemony goodness. I hope to have more in future chapters. Let me know what you think about Calista's origins. I hope I didn't get too out of character with Yukio. ^^" Send in those reviews! Until the next chapter. 3**


	6. Keeping Distant

**Sorry for not updating sooner, I've been busy or just haven't felt like writing. I enjoy this fanfiction and I have some future plans, but I gotta say, I'm getting a little discouraged. I hope you're all enjoying it as well and would love to hear your thoughts and anything you'd like to see happen.**

 **I don't own Blue Exorcist/Ao no Exorcist**

 **I only claim the ocs created for the purpose of this story**

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 **Calist's PoV**

 _"His blood..."_ Calista retreated to her room rather quickly. After that night with Yukio, she had a hard time looking at him without her face turning a bright crimson. It's been days since she drink from him, and still it felt like there was fire coursing through her veins. Was it because he was half demon like her? Or maybe it was because he was Satan's son.

Since that night, she couldn't help seeing him in a different light. Even though he was straight forward and strict, he was sometimes willing to break the rules. He could have easily turned her over to the Order (not that it would have done much good), but instead he offered his own blood to help her. She couldn't hate him for that and in fact was in his debt.

Sitting on her bed, with her back against the wall, Calista closes her eyes, sighing softly to herself, hoping it would clear her mind. When she closed her eyes, the exact opposite happened. Her thoughts didn't clear, instead they shifted back to Yukio. The way his blood tasted on her tongue; spicy but at the same time sweet. It wasn't just the way his blood tasted on her tongue, but the way his scent invaded her senses and made her head spin. The taste of his blood, combined with his scent...she practically melted in his arms.

She was surprised when she heard the softest of moans slip from her throat. So much so, that she opened her eyes wide, her spine stiffening. Grabbing a hold of the sides of her head, Calista shakes it repeatedly. "No, no, no!" She could not begin to feel anything towards Yukio Okumura! Not even a silly crush!

A knock on her door ripped her from her thoughts and she jerked her head up in time to see Rin entering her room, peeking his head around the wall. "Hey, your door was opened a bit so I let myself in. Hope you don't mind."

Clearing her throat, she shakes her head and scoots to the edge of her bed. "I don't. Sorry I was daydreaming a bit and didn't hear you come in."

"No worries, I just wanted to stop in and see if I could borrow your notes from class today." He grins, rubbing the back of his neck. "I kinda fell asleep again and didn't get them all." He chuckles lightly.

She looks at him a moment, staring blankly. _"How in the hell has he even made it this far?"_ She imagined it was just by pure luck, or raw talent. It definitely wasn't because of his studying skills."Yeah sure, let me get them." Getting to her feet, Calista walks over to the desk where her backpack rested on the end of her chair. As she digs through her things, she glances back at him, only to notice he was looking at her things. "If you're going to gawk at a girls stuff, try not to be so obvious."

His eyes went wide, and his face turned red. "I...I u-uh..." Rin crossed his arms and turned his face away, avoiding looking at her and her things. "I wasn't gawking!" He yelled at her, glaring, but she could tell he was embarrassed having been caught.

She laughs out loud, grabbing the papers he needed and handed them over to him. "Don't sweat it, there isn't anything here that I'm worried about you seeing. That stuff I keep hidden away.~" She laughs again at the look on his face as she mentioned this. "You're really easy to pick at, you know!"

"Hey! Cut it out!" He takes the papers from her hand, looking them over a second. "Thanks, Yukio can be a pain in the ass if I don't do any kind of studying." Taking her papers, he turns to leave, but pauses just before exiting her room. "You know, you look a lot better lately."

Her eyes widened. "H-Huh?! What are you talking about?" Now it was her turn to be the aggressive one.

Rin holds his hands up defensively. "I didn't mean anything by it, just that you're looking better than you did when you first got here. I guess you're adjusting quickly." He lifts a hand and waves, leaving her room. "Thanks again!"

Once he was gone, Calista goes to the door and looks out, watching as the oldest Okumura brother walks down the hallway, back towards his own room; his ever present sword on his right shoulder. His words lingered in her mind as she watched him leaving. The fact that she looked better, meant that Yukio's blood had done the job, bringing her back to full health. He didn't mention his brother, or the blood she drank from him, which likely meant Yukio hasn't said anything to his twin.

She sighs, speaking out loud, "Thank God..."

"For what?" Her eyes widened and she spins around to face the familiar voice behind her. How did she not realize he was there?! Immediately, her face turned red and her throat dried up. There must've been something in her expression that worried him, because he suddenly got a look of concern in his teal eyes. "Hey, are you alright?" He asked, taking a step towards her.

As he took a step forward, Calista quickly took a step back, bumping into the door frame. "Y-yeah! I'm fine!" She gains her composure back, recovering the step that she'd taken, holding a fist out to him. "Don't sneak up on me like that! You scared the hell out of me!" Crossing her arms, she puffs out her cheeks, pouting frustratedly.

Yukio gave her a sheepish smile, lifting a hand and rubbing the back of his neck, much like Rin had done just moments ago inside of her room. Even though the two of them weren't identical twins and shared very little in common, there were some gestures that resembled one another and this was one of them. "Heh, sorry about that, but I wasn't exactly trying to sneak up on you." Letting his hand fall back to his side, he looked at her once more with concern. "Are you really okay? Last time you said that, you weren't at all fine. If you nee-."

Calista hurriedly cuts him off, "I don't, and I'm fine, really…" Her arms fall to her sides, bringing her left hand up, she crossed it over her chest and grabbed her right bicep. "I don't need anymore, and from the feeling of it, I won't for a while." She still didn't know what it was about his blood, but she felt like she could easily go a month without needing another drop.

He sighs with relief. "That's great, I'm glad to hear it." There was then a long pause before he speaks again. "If you ever need more…" Another pause, accompanied by a faint, pink, tinting of his cheeks. "Don't be afraid to come to me for help." He says the rest of his statement very quickly, pushing his glasses up his nose again; only this time it seemed to be a reaction made from nervousness, rather than his glasses uncomfortably slipping down his nose.

" _He's kinda cute when he does that.."_ Her thoughts trailed off. Quickly, she shakes her head, and the unwelcome thoughts, from her mind; answering him. "I appreciate your help, Mr. Okumura."

"Yukio…" he said, "Call me Yukio. There's no need to be so formal."

She looked up at him for a moment. _"I shouldn't get too close…"_ Eventually she smiles and nods her head. "Alright, Yukio. Thank you again."He nodded his head, walking passed her, following his older brother. Calista stood there a while more, watching his back as he walked away. _"Keep your distance…"_

But she didn't think she'd be able to take her own advice.

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 **So this is I think my shortest chapter, but I wrote most of it while I took my breaks at work. I have these next two days off, and hope to update again within these two days as long as nothing comes up. Please send in those reviews and let me know if you're enjoying or if you're not, and if not how you feel it could be improved!**


	7. Suspicion

**I'm back! Kinda. Haha. So I know it's been a while since my last update, but I wasn't sure how the next chapter should go. Well I finally figured it out and so here is the next chapter. Every good story need a villain! I'm glad I waited to update, otherwise I likelt wouldn't have been happy with what I did. I'm happy with this and looking forward to further development! Remember to send in those reviews, they keep me going! Enjoy!**

 **I don't own Ao no Exorcist/Blue Exorcist, only the ocs created for the story.**

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Darkness spread throughout the crowded streets of Tokyo. People hurrying from point A to point B. Some going home from a busy day at work, while others were going out to meet friends. Among those unsuspecting humans, a demon of immense power wound his way through them, his deep crimson eyes searching for just the right one; a human to add to his strength, giving him the power he'd need to take down his next prey.

He found what he was looking for in the form of a small female, not paying attention to her surroundings and accidentally bumps into him. She let out a cute little gasp of surprise, falling backwards as she lost her balance.

His speed was among the fastest of his kind and he easily caught her in his arms, keeping her from falling to the ground and dirtying her nice, clean dress.

"I-I'm so sorry!" She yells out a hurried apology, tilting her head up to look at the person she carelessly bumped into. Her eyes widened and her face turned red with embarrassment. He was absolutely beautiful!

Dark green eyes stared down at her from beneath dark brown hair that curled ever so slightly on the ends. His skin was pale, but completely flawless, and his smile…his smile made her feel weak in the knees. When he spoke to her, she felt her breath leave her lungs. "Think nothing of it, my dear." He spoke perfect Japanese, but there was a hint of a foreign accent. Russian, maybe? Still, his voice was enchanting, she could listen to it forever. "You could make it up to me by joining me for dinner, I was just trying to decide where I want to eat, but I'm afraid I am unfamiliar with the best restaurants. I'm not from here and this happens to be my first visit in a very long time."

Of course! She knew the best place to take him, and she'd be more than happy to join him, after all it was the least she could do after she so rudely bumped into him.

Looking down at her, his polite smile turning into a sinister smirk. He had her right where he wanted her; under his spell. Showing her exactly what she wanted in order to get her to go with him. Instead of a demon, she saw a beautiful man, wo harbored no I'll intentions. In reality, she was far from safe. Wrapping an arm around her shoulders, be let her believe that she was leading him to a high end restaurant, and when he pulled her away from the crowds into a deserted alleyway, she never saw the end coming.

 **Yukio's PoV**

"The body of a young female was found this morning…." The tv was open, but Yukio wasn't paying it much attention, at least not at the moment. He ad Rin were in the kitchen, Rin cooking them breakfast, while he sat watching.

It was a Saturday and they didn't have their normal classes today, so they were both out of uniform. It wasn't unusual for Rin, but Yukio seemed to live in either his school uniform or his True Cross Order uniform. His brother might think that he enjoyed it, but come the weekend Yukio was actually glad to be able to wear something a little more comfortable. Though, since he was out of uniform, he also didn't see the need to hide his newly acquired tail either. Having it wrapped around his stomach all day got irritating and itchy. He could see why Rin preferred to keep it out, now that everyone knew about them and their parentage.

He should probably take a lesson from his brother, but he hated his demon side and even more so now that he shared the demonic features with Rin.

"…the body is the second in the last month to be found completely drained off all blood…"

This caught his attention, and as he turned to look at the small television, Yukio felt his heart slow and all the blood from his face drain away, leaving him paler than normal. "Rin, turn that up…"

Briefly Rin looked at his twin brother, before doing as Yukio asked and turns up the volume to the tv.

"…both victims had no visible signs of a struggle, though both were young females around the same age. Police are unsure how they are being drained of their blood, but occult active is the suspected cau-"

Yukio heard enough, reaching over and quickly shutting it off.

"You thinking it's demon related?" Rin asked, though his question went ignored.

Getting up, Yukio heads out of the kitchen. Taking a left he makes his way to Calista's room. All the way thinking it couldn't possibly be her. He fed her himself, she even said it was enough to last her a while. How could she possibly have gone out behind his back? No. She couldn't, it wasn't like her. Cerberus had said the last time she killed anyone while feeding was when she was a small child, unable to control her urges. Still, there was no doubt in his mind that something was going on.

Standing in front of her door, Yukio tried to think about what he was going to say. He didn't want to come off like he was accusing her of anything, but he needed to find out the truth. If she was half vampiric demon, then there had to be others.

He lifted a hand to knock, but hesitated. Maybe he was just reading too much into this and it wasn't demons, but humans foolishly playing around with the occult. No, it was better to be safe than sorry. Shaking his head, he goes to knock on the door, only to find the door opening on its own.

 **Calista's PoV**

She planned on going out and doing a bit of exploring, learning the new place she would temporarily be calling home. It was better to know your surroundings in case things went badly, rather than not knowing and being caught in a dead end, which would likely end your life. So today she was going to learn the ends and outs of not just this school, but the city it resided in.

That was until she opened her bedroom door to find Yukio standing on the other side with his fist up preparing to knock. At first she was surprised to see him, and over the last few days had learned to control her embarrassment over feeding off of him. Still, having him suddenly be standing there caught her off guard and despite her efforts, her cheeks still turned a light shade of red.

"Yukio, what are you doing here?" She questioned. Since the feeding, they haven't really spoken to each other outside of class ad missions. Even living in the same building and spending mealtimes together, they didn't exactly chit chat.

His face went from surprise, to serious in seconds. Something was wrong, but she wasn't sure what. "Have you seen the news?" He asked, letting his hand down to rest at his side.

"The news?" Why would he be asking her if she'd been watching the news? Not sure where this was going, Calista shrugs her shoulders and shakes her head. "No, I just woke up a couple minutes ago. Why?"

He pushed up his glasses, something she was starting to get use to seeing, and jerked his head to the side, indicating he wanted her to follow him. While she didn't see the harm in following, she wasn't so sure she was going to like where it led her.

Calista followed closely behind Yukio as he leads her through the hallway, down towards the kitchen. She could hear Rin talking to his familiar, as well as the sound of cooking going on. By now, she knew that if Rin wasn't on a mission or sleeping, he was in the kitchen cooking something. As they came in, she was able to just briefly see Rin going back and forth behind the counter, but the tv was what caught her entire attention.

There were two pictures, both female, both very pretty. Yukio turned up the volume and she stopped just beside him to listen. The report went on about how both girls were close in age, and that their bodies had been found just days after the other. What made the blood drain from her face was how they had been found.

Completely drained of all their blood…


	8. Slipping

**Sorry the chapters aren't coming out very quickly. With work and everything, it makes it a little harder getting these out. Here's the next chapter, nothing overly exciting, even a little boring possibly. I like developing my characters over time, not just jumping into a ship, I hope you all don't mind the occasional boring chapter like this. Don't worry, the drama and action is coming. There will be romance, there will be pain as well, so don't give up on me just yet! Please remember to send in those reviews! If you have an idea for what I should add to the story, don't hesitate to give me your thoughts and options, they're always welcome!**

 **I don't own Blue Exorcist/Ao no Exorcist or it's characters. I only claim the oc's created for this story.**

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 **Calista's PoV**

"You seriously think I did this!" It only took her a full second to realize why Yukio had been standing outside of her door, why he brought her here and why he was looking down at her with such suspicion. She had once thought his teal eyes were beautiful, but now with the way he was looking at her, she wanted to claw them out. "I don't believe this! I had nothing to do with those girls!"

By now, Rin stopped what he was doing and turned around to look at the two of them. Since Yukio didn't seem to let his brother in on their little secret, there was clear confusion in the older twins eyes. "Yukio, what's going on?" He asked, blue eyes going between the two of them

"I never said I was accusing you," Yukio said with a sigh. "I only asked if you'd seen the news. You're jumping to conclusions.

At this point, she was beyond angry. "You didn't have to say anything, I can see it in your eyes that you're suspicious of me! I haven't done anything like that in years, and if it was me, I damn sure wouldn't do it in a crowded place like Tokyo!" She had enough, turning around, she leaves the kitchen without saying another word.

Marching down the hallway back to her room, Calista couldn't believe for a second that Yukio suspected her of killing those girls. Especially after being told that the last time she accidentally killed anyone was when she was a small child, unable to control her urges. How could he possibly suspect her?! Irritated, she slams the door to her room closed, and let out a contained scream, which sounded more like a squeal.

"What could possibly have you all worked up?" She heard Cerberus speaking in her head.

"That four-eyed spawn of Satan, thinks that I killed two girls over the past two days!" Looking to the hellhound, her aquamarine eyes blazed like fire. "I can't believe he actually thinks I had something to do with it! Ugh!" Throwing up her hands, she drops to the bed. "I never should have revealed my secret to him. Now he's going to constantly think I'm a danger."

The hound stood up, stretched and laid back down again, yawning as he did. "We both know you're not responsible, but the fact remains, someone did kill those girls. I'm assuming since he thinks you did it, then they were drained of their blood." His crimson eyes looked at her from his corner of the room. "Which means, there would appear to be another vampiric demon in Toyko."

He was right. Putting her anger aside, she realized that there was someone out there luring young girls to their deaths. As far as she knew, she was the only demon that needed to drink blood for nourishment. This was the first she'd ever heard of another like her. On the down side, if the Vatican got word of this then she'd be in big trouble. Just like Yukio, they'd immediately suspect her.

Not good.

"Instead of complaining you should probably ask Satan's son for help." After giving his opinion, Cerberus went back to his nap.

She looks over at him from the bed, watching the hound as he fell asleep. Shaking her head, she sits up, hating how he was always right. While she couldn't reveal her involvement with the Vatican, she still needed to enlist Yukio's help or this demon would ruin everything for her and likely end up getting her executed. With a heavy sigh, Calista once more leaves her room, looking for a certain four-eyed, know-it-all.

 **Yukio's PoV**

"Dude, what was that all about?" Rin asked from behind the counter. Obviously watching the exchange between himself and Calista.

Yukio gives a frustrated sigh, folding his arms across his chest. He didn't answer his brother, in fact, he ignores him all together. He needed to figure this all out, and judging by her reaction, she hadn't been at all happy with his accusations, even though he didn't exactly accuse her of anything. Though, bringing her in like that and showing her the news reports probably hadn't been the right way to go about the whole thing.

Still, if he was being honest, a part of him did suspect her. After all, she was literally the first vampire he's ever heard of, much less encountered. Which brought him back to the same question he's been asking since her arrival; just why was she here?

"Oi! Earth to Yukio!" Run calls out to his brother, waving a hand in front of his face.

This had the effect that he wanted, gaining Yukio's attention. Annoyed, he smacks his hand away from him. "Cut it out, Rin."

"Maybe if you weren't off in your own world I wouldn't have to." He crosses his arms. "Now, what the hell was that all about?"

"Don't worry about it, it doesn't concern you." He turns to leave, but was abruptly stopped when Rin grabbed him by the arm.

"Bullshit it isn't! I live here too and I'm getting sick and tired of feeling like I'm being left out of something important!"

Before he got a chance to respond, someone spoke from the kitchen entryway. "You're right, Rin. You shouldn't be left out."

Yukio turned to look at Calista, she didn't seem as upset as she had been when she stormed out just moments ago. Still…"Calista, don't."

She completely ignored him as she walks further in, coming up to the two of them. As she stopped before them, Rin released Yukio's arm. "Alright then, spill it. What's this secret you're keeping, and how does the news report have anything to do with it?"

She looked at Yukio, the expression in her eyes challenging. His own glaring at her, telling not to go any further than she already has. Rin didn't need to know about her being part demon. Despite his obvious displeasure, Calista turns her attention back on his brother. "Yukio thinks that I have something to do with those two girls deaths."

The look on Rin's face was one of confusion, but Yukio could see that suspicion was there too. His posture straightened and his muscles tensed. This girl was a stranger to them, they knew little about her, Rin even less than him. He was starting to put the pieces together and asking the same questions as his brother. Why was she here?

"Why would he suspect you had anything to do with it?" He asked, his arms folding over his chest.

"Because I arrive and all of a sudden two girls are killed. Or, it's probably because I'm a-"

Before she had the chance to finish, Yukio suddenly grabbed her by the arm, pulling her out of the kitchen and into the hallway. He didn't stop there, continuing on until they were in an empty room, shutting the door behind him.

"What the hell, Yukio?!" She yells at him.

With his back to her, she wouldn't have been able to see his jaw was clenched. No way was he going to let her pull his brother into another dangerous situation. They'd just gone up against Satan and things were only just settling down. He needed to keep Rin safe and if she spilled her secret, or that the one who killed those girls was a demon, Rin wouldn't hesitate to put himself in the middle of it all.

Suddenly, he spins around to face her, his teal eyes blazing blue flames. "I'm not going to let you get my brother involved in any of this! He doesn't need to know about you, or whatever connection you have to the demon that killed those girls!"

Yukio watched as Calista took a step backwards, her own eyes wide and reflecting fear. Was she scared of him? Why all of a sudden was she afraid of him? Before he could even question it, he saw her push that fear aside, clench her fists at her side's and take a step towards him. "If you're just going to accuse me of being the one behind it all, then I'm going to go to someone who won't be so quick to judge! Someone who will instead help me figure it out before jumping to conclusions." Calista turns her head, looking away from him. "I thought I could trust you, Yukio, but you're just like everyone else. Seeing the demon before seeing the human." Once more he watched as her hands clenched tight at her side's and when she looked back at him, all the fear from moments ago was gone, replaced with anger. "I'll find this demon on my own, and when I kill him, I'll expect an apology, Mr. Okumura."

With that, she turns on her heel, throwing open the door. Standing there on the other side, Rin looked embarrassed at being caught eavesdropping. How much he actually heard, was unkown. Calista didn't seem to care that he was there, walking right past him, deliberately bumping into his arm as she did.

He didn't bother trying to stop her, feeling his own mixed feelings, fighting to keep his calm, keep his flames under control. His hands were clenched so tight at his side's that he could feel his nails digging into his palms; any tighter and he'd likely start to bleed. She was stubborn and hot headed, just like his damn brother! None of that angered him as much as seeing the fear in the depths of her aquamarine eyes.

Pissed off at not just the situation, but himself, Yukio starts past his older brother, and when he felt Rin grab a hold of his arm to stop him, his control slipped. "Don't touch me!" As he yells, blue flames erupt along his arm, forcing Rin to release him.

Of course this didn't help the situation, angering Rin as well, his jaw clench as he raised a fist to his little brother. "What the hell, Yukio!? You're the one keeping secrets, so don't flare up at me, damnit! Quit leaving me in the dark!"

It took him a minute, but he was able to extinguish the blue flames, calming himself as he knew best; suppressing his emotions. Once the flames were out and he had his control back, Yukio pushed his glasses up his nose. Turning around, he starts walking away. "It doesn't concern you, so stay out of it."

He heard Rin growl his frustration behind him. "You can't keep it from me, Four-eyes!"

By this point, Yukio was completely ignoring his brother, his thoughts back on the demon that killed those girls, and Calista. He couldn't let her drag Rin into this, but he couldn't let her do this on her own either. She was still his student, whether she liked it or not, he would help her…and if it turned out she was the one behind it, he would be the one to kill her.

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 **So as I said, a bit boring, nothing major going on. Still, please send in those reviews and give me your thoughts. Good or bad, I look forward to them all! Until next time!**


	9. Truth Revealed

**Alright, here's the next chapter. Sorry again if this one is once more a bit boring, but I'm working into it upping the drama and bringing in a fight scene soon. Not sure when I'll be able to get the next chapter out, so bare with me.**

 **I don't own Blue Exorcist/Ao no Exorcist**  
 **I only claim the character's created for this story.**

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 **Calista's PoV**

If the demon that killed those girls was in fact like her, than the best bet in finding him would be after sundown. Unlike in the movies, she could go out in the daylight, and it didn't have any ill effect on her. Come sundown though, she did become much stronger, especially after consuming human blood. So it was a safe to assume that the demon would come out either at dusk, or shortly after to feed. That's when she would go in search of him herself.

In the meantime, Calista decided to clean her weapons and focus her mind. She needed to make sure her mind was completely focused on the fight that was likely to take place. She didn't show her weapons often, but they needed a good cleaning. With the three pistols disassembled on the bed, she meticulously cleans them, making certain they were all in proper, working order. It had been a while since she carried all three of them, but tonight she wouldn't be going out as a student, but the full fledged Exorcist that she was.

Much like Yukio, Calista's weapons of choice were pistols, three of them to be exact. Unlike Yukio, she didn't prefer to carry them at the small of her back, instead she wore a shoulder holster that held her two main guns and a holster on her right thigh that held her back up. Between the three of them, she had a total of 73 rounds; not including the extra clips she carried on her side's for quick reload.

Her guns meant a lot to her, they were given to her by the woman who found her. Instead of killing her, she took her in, taught her how to control her vampiric urges. Just before Calista left Rome, she taken her out and bought her the Ruger LC9s that she now carried as her back up on her thigh. The twin Glock 19's had been a gift for becoming an Exorist. Needless to say, these guns meant everything to her.

It took most of the afternoon, but she was putting her last pistol back together as the sun began to set. Looking up towards the window, she watched as the sky changed colors, going from blue to a red/orange. It was a beautiful sunset. "Alright, time to get ready then."

Dressing in a pair of comfortable jeans, Calista first strapped on the thigh holster, making sure it sat comfortably before carrying on. Grabbing a white button up shirt, she left the first two button undone, the white tank top visible. With her shirt on, she opens her closet and pulls out the custom made shoulder holster out, carefully putting it on and making certain it was placed properly, so that it was both comfortable and not in the way. Both her thigh and shoulder holsters on, she puts on her magazine belt. This would allow her quick access to her clips, making it easy to reload her guns in the middle of battle.

Now that her holsters were in place, Calista checks over each of her guns one more time, adding their clips and pulls back the slide, a single bullet being loaded into the chamber. With the safety in place, she holsters the gun. She does this with her two other pistols, making sure each weapon had a bullet in the chamber and was ready, before switching on the safety and adding them to their proper holsters.

Since se couldn't reveal that she was actually here to spy on the twins, she couldn't wear her normal True Cross coat that would conceal her weapons. Instead, she brought along a black trench coat that would have to suffice until she could let her secret out. Thankfully this coat wasn't heavy or cumbersome and would serve it purpose, hiding her guns from the public.

Dressed and ready for a fight, Calista snaps her fingers. When she did this Cerberus immediately woke up from his nap and moved to stand by his master's side. Laying a hand upon the hellhounds head, she spoke without looking at him. "Let's make sure we take care of this bastard before he manages to kill anyone else. We're on our own tonight, so I'm counting on you to watch my back."

She felt his nod his head once. _"I will make certain no harm comes to you. We have a contract, after all."_

"Good, now let's get on with this before either of them catches on to what we're planning. At this time, they should be in the kitchen eating. Be quiet and try not make them aware of us leaving. It'll only make Yukio more suspicious." Again, the hound gives a nod, though this time he didn't comment.

While they still had the chance to leave without being noticed, she opens the door to her room and exits, Cerberus close behind her, waiting as she silently closes the door. Looking left to right, she makes sure the coast was clear before continuing to the stairs and out the front door. Now that she was outside, she gives a sigh of relief, tilting her head down to Cerberus. "This would be so much easier if I'd been able to scout out our surroundings prior to this. I have no idea where I'm going or where the locations of the bodies were found."" This time when she sighs, it was one of frustration. "We're in foreign territories here with no directions."

" _I did tell you to try and recruit the Okumura boy to help us."_ He said, tilting his head to the side a bit, his red eyes looking up at her.

"It's not like I didn't try." She shrugs her shoulder, taking off in a run, heading towards the train that would take her into the main city of Tokyo. "When I tried to tell Rin what was going on, Yukio stopped me. If I'd enlisted his help, I wouldn't have had to go about this alone, but no, Four-eyes just had to step in." Rolling her eyes, she ran as quickly as she could, planning to ride the train from the roof, rather than take her hellhound on the train.

When she arrived at the station, she noticed that they were too early, the train wasn't even here yet. She was a bit out of breath, panting heavily as she tried to catch her breath, Calista looked both ways down the track. "Damn, it doesn't look like it's going to be here any time soon." Pulling the summoning paper out of her coat pocket, she holds it between her fingers. "I'll summon you once I'm in the city." She doing wait for him to protest, ripping the paper in two and breaking the circle. Being a Tamer as well as a Dragoon, Calista could easily summon her demon familiar once more.

With the summoning paper torn, Carberus immediately disappeared in a puff of black smoke. She hated having to do that, and would likely hear about it later when she brought him back, but with the train appearing to be late, she wouldn't be able to jump on like she planned to do earlier and instead needed to wait for it to arrive. "This is such a pain..."

"It's only a pain because you ran off on your own."

 _"That voice..."_ Quickly, she snaps her head to the side, looking behind her, watching as a dark figure approached her from the shadows. "I thought I left without you noticing." Her surprise was evident in her voice.

The light gleamed as he pushed his glasses back into place. "I figured you would do something reckless like this after leaving the way you did this morning, so I decided to keep an extra close eye on you throughout the day." Yukio stepped into the light of the station, wearing his True Cross Order uniform.

 _"Damnit..."_ She didn't even realize that she was being watched, much less being followed. Though, now that he was here, she knew there wasn't any reason to argue with him, knowing that he wouldn't listen to her anyways. Pinching the bridge of her nose, she looks at him. "Fine, but you better be here to help me. I'm not going to have you hovering over my shoulders because you think I'm a threat."

"I wouldn't see you as a treat if you would just come clean about your true reasons in being here." His teal eyes narrowed, glaring at her from behind his glasses. "I know you're hiding at least two guns beneath that coat of yours, and students aren't issued those type of holy weapons just yet."

He really had been watching her, and she underestimated him, thinking she'd been keeping herself secluded enough to go unnoticed. Right now, he had her backed into a corner. Unless she gave him the truth, he would continue to suspect her and that would but innocent in danger, as well as herself.

"Fine," As she started to speak, the train's horn blarred, announcing it's arrival. Even though it was coming to a stop, it still kicked up enough wind to blow open her coat, revealing her guns, even moving her hair around her face. "I wasn't transferred here as a student. I'm an Exorcist First Class. The Vatican sent me here to make sure Satan's powers were kept under control."

The surprise on his face was something she expected, but the betrayal she saw, wasn't. "That's ridiculous! Rin has more control over his flam-!"

"It's not Rin I'm here for," She quickly cuts him off. "You're the one who's under surveillance, Yukio. If I get even the slightest hint that you're a treat, I've been given the order to terminate you, as well as your brother."

His eyes went wide. Those beautiful teal eyes, widened in absolute shock. "Tha...That's impossible..."

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 **I hope you enjoyed this chapter. The truth is finally out. How will Yukio react? How will this affect them? Please. Please. Please, send in those reviews. Give me your honest thoughts on how this story is developing. Until next time~**


	10. Broken Trust

**I'm on a roll. Haha.**  
 **So here is the chapter 10. I don't have a whole lot to say this time, but I really want to encourage you all to send in your reviews. I'm enjoying this story, but I really want to hear your thoughts. Are you liking it? Is there something about it you'd rather change or that I should include? Please let me know.**

 **I don't own Blue Exorcist/Ao no Exorcist**  
 **I only claim the characters created for this story**

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 **Yukio's PoV**

He didn't hear her right. There wasn't any way that the Vatican would suspect him of being a danger. He was an Exorcist, damnit! Since he was seven years old he dedicated his entire life to killing the demons that plague this world, fighting alongside his father; vowing to protect his brother! Just the thought alone pissed him off!

"You've been possessed by Satan once before, what's t say he won't try and possess you again." Her voice pulled him out of his thoughts and he looked back at her. "I've seen how little control you actually have over your flames."

At his side's, his hands clenched into tight fists. "All this time, you've been reporting back to the Vatican." His jaw was clench, making his words sound forced.

"No, I haven't been in contact with HQ since I left Rome."

"You've been lying this entire time, how am I suppose to believe a damn thing you say now?!"

"Listen," she turns away from him, getting onto the train that would take her into the city where the attacks have taken place. "I don't care whether you believe me or not, I have bigger things to worry about. You can choose to help me, if not, then I'm going on my own. Cerberus and I can handle this without you."

He should let her go alone, after lying to him like she had. How can he trust her to have his back in a fight, if she couldn't trust him with the entire truth? As he stood there deciding the train began to pull away, the doors closing. He couldn't trust her after this, but at the same time, he couldn't seem to stand the thought of her going off on her own and being injured. Pulling himself together, Yukio quickly boarded the train, just before the doors closed completely.

When he appeared at her side, Yukio narrowed his eyes on her. "I'm going to make this clear; I don't trust you, especially now that I know the truth. Despite that, I'm going with you, because if I don't and you're hurt or killed, it'll be on my hands for letting you go alone."

Turning his back to her, Yukio faced the door they would exit from once the train comes to a stop. With his back to her, Yukio wouldn't see her smile and nod her head, or the relief in her eyes.

 **Calista's PoV**

She didn't know why, but she felt relieved that Yukio decided to come with her. She knew he was angry, could see that in the way his entire body was stiff, he was just barely keeping a handle on his control. While she wanted to further explain herself, she didn't want to push him any more than she already had. So instead she takes a step back, taking a hold of the metal pole, holding it as the train carried them into Tokyo.

Telling him the truth may have been the worse thing she could have possibly done, but she was honestly getting sick of hiding it. Despite what she'd been told, Yukio and his brother didn't seem like they had any hidden agendas. Rin was stubborn and hot-headed, but he was determined to defeat Satan, constantly trying to better himself in order to be come stronger.

Yukio too only seemed to want what was best for his brother, and while she could see and sense the friction between the twins, there still a bond there. Yukio cared about his brother, even though he made it seem like he hated him. Even still, she could feel that there was a seething hatred underneath it all. Not towards his brother, but towards himself and the demon side he carried. She could understand, after all he had little control over his flames and with all of is suppressed emotions, he would continue to have little control.

Honestly, she felt badly for him. Knowing what it felt like to have no control, always afraid that you'll hurt those around you. Hating the fear in the eyes of your peers. And after living his life as a human for 16 years, only to suddenly become the very thing you hate, would drive anyone over the edge. She was surprised he hasn't been taken over by Satan a second time. He was the perfect example of someone who could become possessed.

For some reason she wanted to help him, she wanted to earn his trust. When she thought about him dealing with his demon side all on his own, whether intentionally or not, it made her heart clench in her chest. Maybe it was because he gave her his blood without even really knowing who she was.

She was suddenly pulled from her thoughts when the doors opened and Yukio started to get off. "We're here, let's go." His voice still had a hint of strain when he talked, but if you weren't listening for it, he would've sounded like his usual self.

Since she didn't know the layout of the city, or where anything was, Calista didn't have much choice, and was forced to follow him. Nodding her head, she quickly exits the train, hurrying to walk beside him.

Now that the truth was out, the tension between them was thick, so much more than it had been after she fed from him that night. For what felt like hours, but was only minutes, they were completely silent. The longer it went on, the more frustrating it started to become. Eventually, she couldn't take it anymore. "Alright, I can't take the silent treatment anymore. At least talk to me about the locations where the bodies had been found. Maybe something on the girls themselves, maybe I can figure out a way to draw the demon out."

At first, she didn't think he was going to answer her, remaining silent for several minutes longer. She was about to speak up again, when he finally glanced over towards her. "The bodies were found in a deserted alleyway the following morning. No one reported them missing and they were found by the homeless. Nothing was taken off of them, they still had all their money and possessions on their persons. There wasn't any physical signs of a fight, no markings whatsoever. They were completely drained of blood, but they can't figure out how the blood had been drained." He sighs and using his index finger, pushed his glasses back up his nose. "They were both females, roughly the same age. There isn't anything else that connects them. They were from different parts of the city, different occupations, though both were described as being beautiful."

As he explained the situation, Calista crosses her arms and nods her head, taking in every detail that she could. "Alright," Unfolding her arms, she starts counting them off with her fingers. "So they were the same age, female, pretty and completely drained of all their blood, but it's uncertain how." Letting her arms fall back to her sides, she gives another nod. "Well, it's safe to say that we're definitely dealing with a demon. Remember when I fed from you?" She glances up at him, just in time to see a faint blush color his cheeks, before he looked away.

"Yeah, what about it?"

"I told you that by morning the puncture marks would no longer be visible and would be completely healed. The reason being, is that there is something in my saliva that heals the wound so that it seems like it was never there to begin with. This makes it easier to take what I need and leave the human none the wiser. They think it was a dream and nothing more. Unfortunately, whoever is doing this isn't just taking what he needs. Also, it's safe to assume we're dealing with a male."

He looks down at her, a questioning look in his eyes. "Why a male? What makes you assume that?"

Calista looked up at him and smiled. "Would you bite the neck of another man or would you prefer one of a hot, young female?" She chuckles lightly, placing her arms behind her neck. "I personally go for the opposite sex, but if I have to, will feed from another girl."

Yukio turned his head so quickly that she wasn't able to read his expression, the light gleaming off his glasses didn't help either. "Yes, well, I suppose that makes sense." He goes silent once more, only to speak a moment later. "Alright, so we're searching for a male demon, anything else?"

"Well, he's likely to be a foreigner like me. Seeing as I'm the first vampiric demon you've encountered, it's safe to say that there aren't any in Japan and if there are, then they're rare and keeping themselves hidden. This one, seems to want to draw attention to himself. So it's likely we're walking into a trap. Don't let your guard down."

He nods his head, stopping as they come up to the opening of an alleyway. "This is the first location where one of the girls was found."

Moving into the alleyway, Calista looked around, trying to find anything that might possibly give her a clue as to who they were dealing with. It didn't take her long before she realized there just wasn't anything here. "Nothing," She sighs heavily in frustration. "Either our demon is very good at cover his tracks, or the police have already taken anything that might help us at all."

Since there wasn't nothing here, she makes her way back to Yukio's side, only to stop mid step as the hairs on the back of her neck stood straight. She looked at her partner, and without speaking a word, knew that he sensed it too.

They were being watched.

* * *

 **Well that was chapter 10, I hope you enjoyed it. I'm looking forward to bringing in our villain next chapter. Hopefully I'll continue my streak and having it out within the next couple days at the least. Remember to send in those reviews! Until next time~**


	11. I won't let you touch her!

**First off, I want to thank those who have and are leaving reviews, they mean a lot to me and I appreciate them! Please keep them coming! I'm so glad you're enjoying my story and I hope you continue to enjoy it.**

 **Now, here's chapter 11! Sorry for not updating sooner, been a little busy. This chapter I'll be bringing in our villain. Things are starting to heat up and become a little more interesting, I'm really looking forward to what's coming. Please remember to send in those reviews!**

 **I don't own Blue Exorcist/Ao no Exorcist**

 **I only claim the characters created for the purpose of this story.**

* * *

 **Yukio's PoV**

The hairs on the back of his neck were standing straight up and even though he couldn't see anyone, he instinctively knew that someone was watching them. After checking out the first scene where one of the girls had been found, he and Calista joined the crowd once more, making their way to the second scene. Only this time they were both on alert.

He glanced down at Calista, walking beside him, holding her hands behind her back. While she looked like she had her guard down, he could tell that she was looking around, trying to get a sense of where their stalker was. How could she possibly act so at ease when they were being followed by the same demon, who just days earlier, killed two women? Then again, she already proved herself to be an adept liar.

His eyes narrowed behind his glasses and he felt his hands involuntarily clench into two tight fists at his sides.

She lied to him and to everyone. Pretending to be just a normal student, when in reality she had been sent by the Vatican to spy on him and his brother. What he couldn't understand, was why this bothered him so damn much! This wasn't the first time someone infiltrated his class and pretended to be one of his students. Shura Kirigakure spent weeks undercover as a male student, spying on Rin for the order. While he'd been pissed about the situation, it didn't even come close to how angry he was about Calista's betrayal.

Suddenly, he felt something or rather someone, flick his glasses, forcing them to go lopsided on his face. He then hears Calista laughing hysterically beside him, using her hand to cover her mouth. His eyebrow twitched, "What is so funny?" He asks, fixing his glasses.

"You had such a serious look on your face that I thought you needed a distraction." She tilts her head, looking up at him with laughter in her eyes. "Flicking your glasses made them go all lopsided, and now your expression is super cute!" She laughs again, doubling over as she did.

Yukio on the other hand, didn't find it as funny as she seemed to. He was just about to tell her to knock it off, when he caught the last part to her sentence. Cute? She thought he looked cute?

Turning his head away, he tries to hide the blush that crept up his neck to color his cheeks. This reaction took his by surprise, still he didn't want to let her see. "Yeah, well, cut it out, we're suppose to be looking for clues."

If she saw him blushing, Calista didn't say anything and after a couple seconds, Yukio was under control once more, with his usual stoic self.

It only took them a few more minutes to reach the next alleyway. "The victims were found only blocks from each other, positioned in nearly the exact same way. Again, both were of course drained of all their blood with no visible signs."

Like before, Yukio watched as Calista walked further into the alley, searching for something that likely wasn't going to be there. As she searched, he kept a look out, standing at the mouth of the alley, looking each way, making It seem like he too was looking clues of his own. What he was really doing, was trying to find who was watching, he could still feel their eyes on them.

He turned his attention back to Calista when he heard her giving an exasperated sigh. "There isn't any thing here either." She said, coming back to stand in front of him.

"Did you expect the results to be any different here than at the first location?"

"No, not really, but I was hoping that our demon would mess up at least a little. A drop of blood, something that could be of use." She crosses her arms. "He's smarter than I hoped."

Like a light turning out, the feeling of being watched disappeared. The tension he felt moments ago, suddenly left his body and he was able to relax. He watched as the same tension left Calista.

"He's gone." She said, lifting her head up to look towards the roof of the building surrounding them. "Alright," He watched as she lifted the sleeve of her jacket, to reveal a summoning tattoo on the underside of her wrist. "How about we take the fight to him now." Bringing her thumb to her mouth, she used her sharp fang to make a small cut along the pad. As blood welled up, she smeared it across the tattoo. "From the depths of the underworld, come forth Cerberus and do my bidding!"

Yukio watched her as summoned her demon hound. This was the first time he really saw her summon the hellhound that normally hung around her freely. He wasn't very skilled at summoning and controlling demons, but he could if he really needed to. Calista however, held a meister in being a Tamer, so where it took a lot for him, she made it look easy.

"Listen up, Cerberus, I need you to catch that demons scent and track him down. He was just here, so it shouldn't be too difficult for you to find his trail." When she gave him the command, she took on a demeanor he hadn't seen from her before. It wasn't her usual laid back self, but one of authority.

With a single nod, the hound leaps to the roof of the building. Before he could question her, Calista was climbing up the fire escape that would lead to the roof to their right. "Hey! What are you doing?!" He yelled out, grabbing the edge of her coat before she could get out of his reach.

When she looked down at him, the expression on her face said it was a no-brainer. "Hell hounds have an exceptional sense of smell, 20x better than that of a mortal hound. It won't take Cerberus long to pick up the scent of our killer and once he does, he'll lead me right to him. Then I'm going to defeat him."

"You can't go up against him on your own. I know I made it clear that Exorcists don't work alone." He released her coat. "You may not be a real student, but surely you know that number one rule."

He watched as she rolls her eyes. "Fine," she starts back up the ladder. "Come on then. I'm going with or without you, Teach." She didn't wait for him, climbing the rest of the way up and disappearing over the side, following her hound to the roof.

"Damnit," Yukio mumbles to himself. "She's just as stubborn as Rin." Still, he follows her up the fire escape and on to the roof.

Once he was on the roof, Yukio straightens his clothes and glasses. Looking around, he spots Calista on the other side, talking to her familiar, who had his nose to the ground.

"I thoug-" He didn't get the chance to say anything, as the hell hound lifted his head and took off, jumping over to another roof, heading east.

"He's got the scent. Try and keep up, Four-eyes!" Just as quickly, Calista follows, jumping easily to the opposite roof, keeping up with her demon.

His jaw clenched and so did his fists. If he didn't keep up with her, she would leave him in the dust. "Tch," Taking off in a run, Yukio just as easily leaps across, catching up to her and running alongside. He glanced over in time to see her give him a teasing smirk.

They ran on the roofs of the buildings, leaping easily from one to the other. Since they were both half demons, their endurance and strength far outweighed a normal human's and as long as the roofs weren't too far apart, they would manage easy enough. It didn't take him long to figure out that they were heading away from the busy city.

" _Well, at least we won't need to worry about hurting anyone."_ He thought to himself as they came off the rooftops and back to solid ground.

"Yukio, watch out!" Calista's warning brought him back to his senses.

The threat was coming from above and if he didn't react quickly, Yukio would end up being hit by whatever was coming down on top of him. Pivoting his foot, he changes direction, jumping to the right, pulling both of his pistols from behind his back; just in time to hear a loud thud, followed directly by a cloud of dust.

Calista soon appeared at his left side, in her hands were a set of matching pistols like him; only hers were smaller to better fit her hands. _"So she's a Dragoon as well as a Tamer…"_

"Get your head in the game, Okumura, it would appear that he knew all along that we would follow him." Her eyes were completely focused as she aimed her guns towards the cloud of dust. "He led us here."

She was right. He needed to get his act together and focus on what was happening here and now. If he didn't keep his head straight, they were both likely to be hurt, or killed. Turning his attention on the cloud as it began to dissipate, his guns aimed at the center.

Someone began to laugh, the sound deep and distinctly male. "My, my, you are an intelligent young Exorcist. You figured it out all on your own and much faster than I thought you would too." He spoke with an accent, one Yukio didn't recognize.

Gripping the butt of his pistols more tightly, his fingers resting on the triggers, ready to fire, he addressed the male before them. "You are accused of killing two human women, and will be taken into custody. If you come quietly, we will not use force."

As the dust settles, a man appeared in the center of a small crater. He was tall, much taller than him, with black/blue hair that closely resembled Rin's. His eyes were a deep shade of crimson, that stood out against his unusually pale skin. Given the assumption that this demon was just like Calista, it was safe to say that he hasn't seen much daylight, preferring the night.

He didn't give Yukio an ounce of his attention, despite him talking directly to the man. Instead, his sole focus seemed to be on the female at his side. "You've grown into quite the beautiful young lady. I must say, you look like an almost exact copy of your mother."

From the corner of his eye, Yukio saw Calista suddenly stiffen. "I don't know who you think I am, but I can guarantee you don't know my mother and I know for a fact you don't know me."

"You certainly sound confident in that," He smirks, and when he did, he saw just a hint of fang; even shaper than Calista's. "Abandoned as a child, left all alone to fend for yourself." As he spoke to her, he began to walk forward.

"Don't move, damnit!" Yukio yells, his muscles tense as he steadied his aim. Again, Yukio seemed to be ignored completely.

"An unquenchable thirst for human blood," He continued to make his way to Calista, and Yukio could see that her hands were trembling. "Killing an entire village before being found and nearly killed by the very same Exorcist that took you in." He was within reach of her and extended his hand to touch her cheek. "I know everything about yo-"

Suddenly he was cut off as a loud "bang" echoed off the walls of surrounding buildings. A large hole could be seen in the center of the demon's hand where his palm had been, preventing him from actually making contact with Calista. Quickly, he jumps back, putting several yards between him and the Exorcists, his crimson gaze finally turning and acknowledging the boy.

"I told you not to move, damnit!" Yukio yelled out, smoke rose from the barrel at the end of his gun. "I won't let you touch her."

He could just make out the shocked expression on Calista's face, her eyes wide as she looked at him, her weapons lowering. "Y-Yukio…"

Across from them, the demon's eyes were narrowed in anger and hatred. "You damn brat," Yukio heard him say between clenched teeth. "You're in my way."

He didn't take his aim or eyes off the male, ready to fire a second time if he took another step towards them. "Move again, and the next shot will end your life."

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 **So this chapter was completely in Yukio's Pov. Next chapter we'll be returning to Calista's to get her take on the situation. Who do you think the demon is and what might his connection be to Calista? He seems to know quite a bit about her, huh?**

 **If there are any errors, I will correct them as I find them. I tend to write late at night, just before bed or during my free time while working and don't always catch mistakes until I've reread it after posting. Feel free to point any out.**

 **Remember to send in those reviews!**

 **Until next time~**


	12. Is This the End?

**So this is likely my shortest chapter yet. Not something I will do often, or try not to. I wan to once again thank those who are taking the time to leave me reviews, they are much appreciated. Please continue to leave them.**

 **I don't own Blue Exorcist/Ao no Exorcist**

 **I only claim those created for this story**

* * *

 **Calista's PoV**

She was frozen in place. His hand was reaching out towards her. He was going to touch her! She couldn't let his hand touch her cheek. So why wasn't she moving?!

"Shoot damnit!" Calista yelled at herself. But her finger didn't squeeze the trigger. Instead, her hands trembled. "Shoot him!"

BANG!

A gun shot rang out, a nearly deafening sound.

Did she actually pull the trigger? No. She didn't do it. So that meant…

"I told you not to move, damnit!" Her eyes widened as she turned her head to look towards Yukio at her side. Smoke rising from the barrel of his pistol. "I won't let you touch her."

"Y-Yukio..." Calista completely forgot that she wasn't here alone. Lowering her weapons, she watched him for a moment, twice now he's come to her aide. If he hadn't of taken that shot before the demon's hand touched her, she didn't know what would have happened. For a minute there, she felt herself lowering her guard and even curious how he knew so much about her, wanting to know if he truly had known her mother.

"Snap out of it." Immediately, Yukio snapped her focus back. "Don't let him get to you. Remember a demon will do anything to give them the advantage."

He was right, of course and with a firm nod, she brought her pistols back up, aiming them directly at his head. "As Exorcists of the True Cross Order, you're under arrest for the murder of two human females. Come quietly or we will be forced to take you in by other means." Was her voice trembling? Her hands gripped the butts of both her guns, trying her best to regain her composure.

An ominous feeling came over her.

"I'll give you that one, boy, but you won't be getting another one." His voice was deeper than it had been before, giving away just how much Yukio's shot ticked him off. "As for you, my dear," Crimson eyes turned their attention back to her, making her blood run cold. "I will take you for my own sooner or later." He may be looking directly at her, but it was clear that he was no longer ignoring Yukio's presence.

"Shut your mouth!" She yells out, her emotions slipping through. "I don't know what you're talking about, but I will be going nowhere with you."

Despite Yukio's bullets being specifically designed to combat and wound demons, the hole in the center of his palm began to heal right in front of their eyes. Before long, the wound was completely closed, only the traces of blood gave any indication that there had been significant damage done. "Everything will be made clear in due time, scumpa mea." He turns around as if to leave them. "You will eventually come to me of your own free will."

"Stop!" Yukio yells put, taking a step forward, at the same time firing three rounds. But the demon wasn't there any more. He moved so quickly that neither of them saw where he went.

He suddenly appeared in between the two of them, crimson eyes burning with hatred. "I did tell you I would only give you one shot." Too quick to react, the demon spun around, delivering a hard kick to Yukio's unguarded side. He didn't have a chance to fire another shot, the kick sending him flying to the other side of the field they were lead to.

"Yukio!" She calls out to her partner, turning her own weapons on the demon and firing multiple rounds, emptying one clip. Hitting the release, she drops the magazine. Before it hits the ground, she had a new one in place.

It didn't matter though, he dodged every bullet she fired at him. His hand wrapped itself around her throat and as he slammed her back against a stone wall, the wind was knocked out of her chest. Instinctively, she drops her guns and tries with both hands to force him to release her throat. Her nails dig into his skin, but it did little good as he only tightened his hold on her.

As he leaned in close, she could see that his fangs were sharp and elongated. "I was going to wait to taste your blood, but I think I will do so now instead." He growled his words, moving his hand just slightly to the side, exposing the vital part of her neck. Forcing her to tilt her head, giving him a better angle, leaning in even closer.

She could feel his hot breath against her skin and knew she couldn't let him bite her. If he did, she feared what would happen next. She needed to reach the Ruger she had strapped to her thigh. Calista let her hand drop to her side, making it seem like she wasn't able to hold it up any longer, and reached for the smaller weapon. If she could just get her back up gun, she could shoot him in the head while he was distracted.

His lips were against her skin now, and she felt his tongue lick along her carotid artery. A scared whimper comes up from her throat, she was so close to her gun, could feel it at the tips of her fingers, but her arm was just too short to fully reach. His sharp fangs scrape across her skin, ready to puncture.

Squeezing her eyes shut, Calista cried out in her head for someone to help her, she didn't want it to end like this. Just before his fangs penetrated her throat, she found herself falling a short distance to the ground below. With his hand no longer cutting off her airway, she was able to suck in much needed oxygen, her lungs quickly expanding as she gasps. As soon as she gasps, she begins coughing, her hands holding her sore and likely bruised neck.

Opening her eyes, she looks up to see what stopped him from fully biting her. She was momentarily blinded by a bright blue light. It took her a second to realize that the bright blue light was actually blue flames. Satan's blue flames, and standing in front of her, between the demon and herself, was Rin Okumura, his sword drawn.

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 **I'm a sucker for a cliffhanger. Normally I wouldn't end the chapter this short, but I like leaving a chapter in a way that makes people guess what's going to happen next. If you've read some of my previous stories, you know I tend to leave a chapter with a cliffhanger. This seemed like the perfect opportunity to bring in Rin, because even though this is a story centered around Yukio, Rin is still the main character of Blue Exorcist. Besides, did you really think Rin was going to just let his little brother leave him behind like that? Until next time~**


	13. Fear

**So this one is longer than the one before. I hope you'll enjoy this like the others. I've been pretty busy so I'm sorry for not updating sooner. I want to thank those who are taking the time to write and send in their reviews, you guys are my heros! I love feedback of any kind, so PLEASE keep them coming! I don't know when I'll be able to update again, so bare with me. If there are any errors, I will fix them when I go back and edit the chapter.**

 **I don't know Blue Exorcist/Ao no Exorcist**  
 **I only claim those created for this story**

* * *

 **Calista's PoV**

Blue eyes looked back over his shoulder, narrowed on her as she sat on the ground trying desperately to catch her breath. Her throat hurt to touch, but she knew come morning, it would be as if nothing ever happened. "R-Rin…" She winced as she tried to talk, his name only coming out as a hoarse squeak.

"Just shut it," He said, turning his attention back to the demon. She could see now that he was cradling his arm against his chest, and while the limp wasn't completely severed, it wasn't all the way on either. "After I've kicked his ass, you and Yukio can explain everything." With a yell, he rushes forward to engage the enemy.

From the ground, she watched as the oldest twin fought back against the vampire. Still, the vampire was strong and dodged or countered each swing of the sword, even injured as he was. Though, it seemed he was on the offensive, doing his best to keep away from those blue flames.

"Calista!" Someone yelled her name.

"H-huh…" She turned her head in time to see Yukio running up beside her, skidding in the dirt, his gun still in his hand. "Yu-"

"Don't talk," He immediately cut her off. Putting his gun in the holster at his back, he reached out his hands, touching her neck. Whereas the vampire had been forceful, cutting off her airway, Yukio's hands were gentle and warm, looking over her injury. She'd forgotten he was also a doctor. "Are you alright?"

Was that actual concern in his voice? She quickly dismisses the thought and nods her head. Since it hurt too much to talk, and Yukio told her not to do so anyways. His eyes looked her over, his hand touching her throat and seeming to pay close attention to the spot where the vampire had nearly bitten her. The way he touched her, made it seem like he might actually care whether or not she'd been hurt.

Bringing her hands up, she grabs a hold of his wrists. When he paused and looked at her, she shook her head, pushing his hands away with a small smile. "I'm alright, Yukio, go and help Rin." Calista says in a soft voice, even though it caused her discomfort to say anything.

He looked at her a moment more, and she could now see that the right lens of his glasses were cracked. The concern fades from his eyes and as they narrowed, anger flared up in their depths. The teal coloring darkened and took on a more blue tint, comparable to Rin's. "Right, just stay here." Getting back to his feet, Yukio takes off to help his brother, his hands disappearing behind his back just long enough to pull the pistols from their holsters.

Calista watched Yukio rush off to stand beside his brother. Together the twins worked to corner the demon. Shots rang out, echoing off the building walls. Blue flames lit up the entire area, casting a blue light over everything. Even though Yukio played it off like he wasn't overly fond of his brother, the two of them worked together better than most. They didn't need to speak to each other, reading the others movements and body language. Yukio knew when he would throw his flames and Rin knew when to jump out of the way of Yukio's bullets. It was actually really incredible to watch.

As she watched the two of them fighting side by side, Calista began to feel weak compared to them. Looking around, she tried to spot her familiar. _"Where the hell are you, Cerberus?"_ She questioned, worried about the hound. He'd been ahead of them, and it was possible that the vampire had injured him before they were able to catch up.

Her hands curled up in her lap. She couldn't just sit here and do nothing, while the twins were fighting. Deciding that she wouldn't just stand by, Calista spotted her guns. Grabbing them both, she gets to her feet, planning to join Yukio and Rin. Her knees shook, whether from fear or still not at 100% after being choked, she didn't know for sure. Either way, she wasn't the type to let others fight her battles. With the three of them working together, they should be able to quickly over power and defeat him.

Unfortunately, by the time she gained her courage, the sounds of gunfire ceased and the bright glow of blue flames disappeared, casting the area in darkness once more. Was the fight over? Did the Okumura brothers defeat the demon? Turning her head side to side, she looks for the twins, finding them on the other side of the empty lot, speaking to each other.

Holstering her guns, she runs over to them. "What happened? Did you beat him?" She calls out.

Yukio looked back over his shoulder at her, his eyes once more that beautiful shade of teal. "No."

"The damn coward took off." Rin spoke up, his sheathed blade over his right shoulder. "He didn't even try to attack back, defending himself and then running off."

Hearing that he got away, a chill went down her spine and she felt the blood drain from her face. Her knees suddenly give out and she falls to the ground. Calista expected to hit the ground hard, but instead she felt a pair of arms wrapping around her, catching her before she met the hard surface.

Fear. There was no doubt about it now, this was fear. She was terrified of this strange demon, of how much he knew about her. Her vision began to tunnel, as the fear overwhelmed her. Before she could even attempt to fight against it, she completely blacked out.

 **Yukio's PoV**

From across the bedroom, Yukio stood with his back against the wall, his arms folded over his chest. His coat lay over the back of Calista's chair, thrown there haphazardly, forgotten in the moment. The room had no lights on, but Yukio could see perfectly; watching as the female rested in the bed just feet from him.

Given the circumstances, some might think he was here just keeping an eye on her, having admitted to being a spy for the Vatican. This wasn't the case. Instead of watching over her for being a spy, Yukio stood watch over her, worried about her health. After she blacked out, Rin had offered to carry her back to the dorms, but Yukio wouldn't allow his brother to do so, taking it upon himself to take her back, to see over her and tend to her injuries.

His glasses began to slip down his nose. Normally he would immediately push them back into place, but his entire focus was on Calista. While her breathing was no longer ragged and labored, and the bruising on her throat was fading, she still hasn't woken up. It's been hours now, and the morning's first light would soon shine through the window.

He had a class to teach this afternoon, and his own classes this morning. Still, he didn't want to leave her like this and she suddenly take a turn for the worse. With his jaw clenched, Yukio takes a step towards her, finally adjusting his glasses. Standing beside her, he looks directly down, looking her over. Her color looked good, she showed signs that she wouldn't fully recover. If she had healing properties like he and Rin did, than by tomorrow she should be back to her old self.

Sighing heavily, he sits down on the floor beside the bed. Exhausted after fighting against the demon, then staying up all night watching over her, he could feel his eyes were heavy. Using his arm to prop his head up, Yukio rested his head, closing his eyes. He'll close his eyes for a few minutes, just long enough to recollect his thoughts. Then he'll have to leave her to get ready for school; coming back to check on her every chance he got.

"Yukio.." He could hear someone calling his name. "Wake up, Yukio." Along with his name being called, Yukio felt someone gently shaking his shoulder.

When he opened his eyes, Yukio blinked a couple time. Only, no amount of blinking would chase away the blurriness of the room **(Does anyone know just how bad Yukio's eye-sight really is?)**. Scowling, he lifts his head, flinching at the stiffness of his neck and back. How long had he been out? "Where are my-"

"Here," He was cut off by a soft voice coming from his right. "You looked exhausted and I figured your glasses weren't very comfortable to sleep in, so I took them off."

He could make out his glasses being held out for him, and taking them he put them on, instantly clearing his vision and allowing him to see once more. Looking around, he realizes that he was still in Calista's room, sitting on the floor where he sat down moments ago. He frowns, taking note the light filtering in from the window.

It was too bright to be early morning...

"What time is it?" He asks, sitting straighter and stretching his stiff back. "How long was I out?"

"It's close to two in the afternoon." His eyes widened as she said this. "I woke up about an hour ago. When I saw you sleeping, you looked so peaceful that I thought to just leave you alone."Her words trailed off, soon falling on deaf ears.

He was so late! Yukio quickly jumps to his feet, stumbling a bit his feet tingling and numb from sitting on the floor for so long. He jumps around trying to gain feeling again, grabbing for his jacket, instead it get caught on something and as he goes to pull back on it, the chair tips over. With his feet tingling as they were, he couldn't keep his balance and ends up falling over.

From the bed he could hear her muffled laughter. Looking over at her, he shoots her a deadly glare...which did nothing to make her stop laughing at him. Rolling his eyes, he gets back to his feet, the feeling in his feet finally back enough to allow him to stand without feeling like he was standing on pins and needles. "Shut it," He forcefully pulls on his jacket, embarrassed now. "I completely skipped classes today and I'm due to teach as well. I was only suppose to close my eyes for a few minutes." Yukio was mostly mumbling to himself now, annoyed that he over slept.

"Calm down," Calista said, now sitting on the edge of the bed with her feet touching the floor. "Last night was hectic, it's no wonder you were exhausted. You obviously needed the sleep or you wouldn't of fallen asleep like you did." She shrugs her shoulders, standing up and stretching her arms above her head. She only wore her shirt and jeans, Yukio removing her jacket and gun holster when he brought her back. "Especially since you were able to fall asleep in such an awkward position."

Seeing her stretching, Yukio slowed down a bit. Instead of putting his jacket on with force, he now pulled it on more easily. Mostly because he was taking in her appearance and health. "How are you feeling? You passed out after the fight last night."

She looked over at him. "I feel fine, actually. I'm pretty sure that I'm all healed up." Tilting her head a little, she looks at him questioningly. "Yukio, why did you stay here with me all night?"

He looks away, hiding the blush that he felt creeping up to his cheeks. "I wanted to make sure you were alright. That you didn't take a turn for the worse in the middle of the night."

"I didn't think you'd really care."

His head turns quickly towards her. "What? Why the hell would you think that? Of course I'd care." Shaking his head he goes to the door, pausing just a moment to look back at her. "No worry about coming to classes today, just stay and get some rest. You're looking a little pale again." After giving her his orders, Yukio leaves her room, closing the door behind him.

* * *

 **Not sure how I feel about this chapter. I like it and I don't at the same time. The enemy is still on the loose. What will that mean for Calista? Just how much does he actually know about her, and what are his plans? Yukio seems to be coming around, openly admitted he cares. Remember to send in those reviews!**  
 **Until next time~**


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